RM250 platform for Snowbike?

wwillf01

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I guess we are lucky we ride very little road and are straight into the trees .

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May 26, 2020
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Yeah that does sound good. We have access roads to get to higher country. You can choose to ride the road or rip around in the trees and meadows to get to the same place.

Ultimately I want to use this to explore the high country. I'm not that interested in boon docking trees all day. I watch the YouTube videos of guys doing that and it puts me to sleep. I want to get into the alpine and rip around at 10-11,000'! I hope I can get this bike there...
 
May 26, 2020
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Well you could even try a ktm 13t on the bottom if you want to go really fast. You will probably have to take a link out of the chain to make the smaller sprocket work.
It's not that all I want is top speed, I just want to be able to go anywhere...

I heard back from Eiliff at moto Trax - he's been super helpful answering any questions I have. He said it was OK to grind down the chain guide in the track a bit to get a 14T on the CS. I think I'll start there.

Eric, do you know which sprocket has more effect: the CS or the driveshaft on the track? I know on dirt bikes 1 tooth on the CS is about 2-3 teeth difference on the rear sprocket.

Thanks for the advice guys.
 
Dec 19, 2007
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It is based on percentage of change. On a bike it's about 1-3 ratio because the rear has 3 times the teeth so a tooth on the rear is a much smaller percent of change in tooth count then front. Snow bike sprockets are all closer to the same size but changing a tooth on the smallest one will still make the biggest percent of change.
 
May 26, 2020
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OK guys, I'm totally frustrated. My RM295 snowbijke project is still that... a project! It's almost March and I'm still not riding. A few days ago I had enough and went an purchased a used Summit 850. I don't want a project, I want to ride!

Here's where I'm at:

The track - the track is a used Moto Trax 129. The bulkhead bolts used to adjust primary chain tension are seized. So my only adjustment is in the nautical washers that adjust both primary and secondary chains. I bumped my CS sprocket up to a 14T which required some grinding on the chain guide to get it to fit, then had to add a half link on the primary chain to get the tension right on both chains (remember no adjustment in bulkhead bolts). That all seems pretty good, but spinning the track while on a stand I noticed that it goes from spinning freely to quite a bit of resistance. Upon closer inspection I'm finding the secondary chain tension goes from being within spec to overly tight with the rotation... So something is out of round... Any ideas?

The bike - as mentioned before is a 2002 RM 250 that I had Millennium tech punch out to 295. I bought it from a friend. It was Rich Taylor's bike in the beginning and had several aftermarket Pro Circuit stuff on it. It did not come with a title and I was told it was a 2004. I have a 2006 rm250 that is my trail bike, so I was psyched the parts would be compatible. Upon seeing the bike I determined it was not an '04, and looking at the front suspension and routing of the brake line, I thought it was an '03. I sent it off to Millennium Tech for the Big Bore kit for an '03 RM. Millennium tore into it, then had some issues after overboring it. We talked on the phone, they asked if I was sure it was an '03, I wasn't 100%, so I looked up the serial number. Turns out it's an '02 with an '03 front end on it... They hummed and hawed for quite a while, thinking the overbore was not going to work on that cylinder. They began looking for a new cylinder for me. Then I get a call and they had one of their 2 stroke gurus check it out and he said, no problem, just run this KX head gasket on it and you'll be good. Sweet, I think. They send it back and I bolt the whole thing up - more on this later.
When I got the bike running on New Years it would start after several kicks, idle great and the cooling/heated carb & bars seemed to all work well. I'm running C3's thermostat, carb heater, bars and push to fit fittings. When on the snow it felt like the clutch was slipping at mid to upper RPMs. I had no track speed. Thinking this was gearing, I did the 14T sprocket swap, but my gut was saying clutch. I had rebuilt the clutch with a Wiseco basket, new OEM springs and friction plates. After several short test rides I talked to a mechanic buddy of mine who suggested HD clutch springs. I ordered those and swapped them out, which seemed to help, a little.
In addition, when running the bike under any sort of load or speed, I'm getting a loud "knocking" sound coming from the engine. I'm worried that I'm possibly getting piston contact with the head, and Millennium's "fix" may have not been successful.
After installing new clutch springs, 14T sprocket and engine covers I took it out for a test ride with 3-4' of new snow. It fired up after a half a dozen kicks, warmed it up to 100* and tore into the deep. It seemed to run well, plowing through the light snow in 2 and 3 gear. Temps were all good in the 120-130 range. After 15 minutes I got some sputtering, pulled over and noticed the intake (velocity stack with skinz cover) was buried in snow. I scooped it out and carried on. A few minutes later, more sputtering, but the intake was more or less snow free. At this point my idle was sputtering and I thought I should return to the car before she died. At the car, when shut off, I noticed the snow melting off the engine was discolored. When I got home and removed the skid plate, a huge wad of gunk splatted on the floor, having come out of one of the power valve breather tubes...
After a week of it sitting in the garage, I went to start it up. No dice. After 30 minutes of kicking and frustration I went to pull the plug and noticed it was only hand tight - I had been leaking compression, which probably explained why some of the poor running issues. Also, the plug looked cooked - the aluminum was discolored, the gap was way out of spec too big, and there was lots of oil/grease on the fitting where the cap pops on. A few kicks with the plug off to clear some of the flooded gas, a new plug gapped and she fired up again.
I took it for another test ride close to home in some funky 2-3' bottomless snow with a sun crust on it, but again it felt like the clutch was slipping - no track speed at upper RPMs. In addition my temps were sky rocketing. With the engine covers and funky snow, almost no snow was getting on the engine, speeds were low, so very little air moving through the rads, yet the engine was revving hard. And still the "knocking" sound. Back to the garage.
It sat for a week while I had work and no time. Then the other day I go to start it up to warm up the engine for an oil change and I can't get it to start. I pulled the plug again but the plug looked great. Maybe flooded, but certainly not fouled and within spec. I kicked for 10 minutes and gave up. Two days later I bought a sled.

Here's what I'm thinking: I got scammed on the track, as I was told it had been ridden one season and rebuilt with new hifax. Turns out this thing was abused in some way and something in the drive shaft is out of spec. As far as the bike, I worried that Millennium Tech's "fix" is not complete and somethings just not right with the overbore. I think the HD springs have helped my slipping clutch but maybe I fried the friction plates on the 3 or so rides before the HD springs. But why won't the bike start anymore? Why does get flooded when I'm applying no throttle at start up? Lots of unknowns for me...
I know these things take some tuning and work. I also realize that nearly everyone is a custom job, but I'm totally frustrated. My mechanic friend rides a YZ450f in winter and YZ250s in summer, but he's out of town dirt biking in the desert. I really want to get this thing to work, but I'm close to throwing in the towel. However, I've got a lot invested in it - the bike was cheap, the track was affordable but all the aftermarket work and parts have added up. Any help would be appreciated.
 

tribalbc

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Jan 26, 2019
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OK guys, I'm totally frustrated. My RM295 snowbijke project is still that... a project! It's almost March and I'm still not riding. A few days ago I had enough and went an purchased a used Summit 850. I don't want a project, I want to ride!

Here's where I'm at:

The track - the track is a used Moto Trax 129. The bulkhead bolts used to adjust primary chain tension are seized. So my only adjustment is in the nautical washers that adjust both primary and secondary chains. I bumped my CS sprocket up to a 14T which required some grinding on the chain guide to get it to fit, then had to add a half link on the primary chain to get the tension right on both chains (remember no adjustment in bulkhead bolts). That all seems pretty good, but spinning the track while on a stand I noticed that it goes from spinning freely to quite a bit of resistance. Upon closer inspection I'm finding the secondary chain tension goes from being within spec to overly tight with the rotation... So something is out of round... Any ideas?

The bike - as mentioned before is a 2002 RM 250 that I had Millennium tech punch out to 295. I bought it from a friend. It was Rich Taylor's bike in the beginning and had several aftermarket Pro Circuit stuff on it. It did not come with a title and I was told it was a 2004. I have a 2006 rm250 that is my trail bike, so I was psyched the parts would be compatible. Upon seeing the bike I determined it was not an '04, and looking at the front suspension and routing of the brake line, I thought it was an '03. I sent it off to Millennium Tech for the Big Bore kit for an '03 RM. Millennium tore into it, then had some issues after overboring it. We talked on the phone, they asked if I was sure it was an '03, I wasn't 100%, so I looked up the serial number. Turns out it's an '02 with an '03 front end on it... They hummed and hawed for quite a while, thinking the overbore was not going to work on that cylinder. They began looking for a new cylinder for me. Then I get a call and they had one of their 2 stroke gurus check it out and he said, no problem, just run this KX head gasket on it and you'll be good. Sweet, I think. They send it back and I bolt the whole thing up - more on this later.
When I got the bike running on New Years it would start after several kicks, idle great and the cooling/heated carb & bars seemed to all work well. I'm running C3's thermostat, carb heater, bars and push to fit fittings. When on the snow it felt like the clutch was slipping at mid to upper RPMs. I had no track speed. Thinking this was gearing, I did the 14T sprocket swap, but my gut was saying clutch. I had rebuilt the clutch with a Wiseco basket, new OEM springs and friction plates. After several short test rides I talked to a mechanic buddy of mine who suggested HD clutch springs. I ordered those and swapped them out, which seemed to help, a little.
In addition, when running the bike under any sort of load or speed, I'm getting a loud "knocking" sound coming from the engine. I'm worried that I'm possibly getting piston contact with the head, and Millennium's "fix" may have not been successful.
After installing new clutch springs, 14T sprocket and engine covers I took it out for a test ride with 3-4' of new snow. It fired up after a half a dozen kicks, warmed it up to 100* and tore into the deep. It seemed to run well, plowing through the light snow in 2 and 3 gear. Temps were all good in the 120-130 range. After 15 minutes I got some sputtering, pulled over and noticed the intake (velocity stack with skinz cover) was buried in snow. I scooped it out and carried on. A few minutes later, more sputtering, but the intake was more or less snow free. At this point my idle was sputtering and I thought I should return to the car before she died. At the car, when shut off, I noticed the snow melting off the engine was discolored. When I got home and removed the skid plate, a huge wad of gunk splatted on the floor, having come out of one of the power valve breather tubes...
After a week of it sitting in the garage, I went to start it up. No dice. After 30 minutes of kicking and frustration I went to pull the plug and noticed it was only hand tight - I had been leaking compression, which probably explained why some of the poor running issues. Also, the plug looked cooked - the aluminum was discolored, the gap was way out of spec too big, and there was lots of oil/grease on the fitting where the cap pops on. A few kicks with the plug off to clear some of the flooded gas, a new plug gapped and she fired up again.
I took it for another test ride close to home in some funky 2-3' bottomless snow with a sun crust on it, but again it felt like the clutch was slipping - no track speed at upper RPMs. In addition my temps were sky rocketing. With the engine covers and funky snow, almost no snow was getting on the engine, speeds were low, so very little air moving through the rads, yet the engine was revving hard. And still the "knocking" sound. Back to the garage.
It sat for a week while I had work and no time. Then the other day I go to start it up to warm up the engine for an oil change and I can't get it to start. I pulled the plug again but the plug looked great. Maybe flooded, but certainly not fouled and within spec. I kicked for 10 minutes and gave up. Two days later I bought a sled.

Here's what I'm thinking: I got scammed on the track, as I was told it had been ridden one season and rebuilt with new hifax. Turns out this thing was abused in some way and something in the drive shaft is out of spec. As far as the bike, I worried that Millennium Tech's "fix" is not complete and somethings just not right with the overbore. I think the HD springs have helped my slipping clutch but maybe I fried the friction plates on the 3 or so rides before the HD springs. But why won't the bike start anymore? Why does get flooded when I'm applying no throttle at start up? Lots of unknowns for me...
I know these things take some tuning and work. I also realize that nearly everyone is a custom job, but I'm totally frustrated. My mechanic friend rides a YZ450f in winter and YZ250s in summer, but he's out of town dirt biking in the desert. I really want to get this thing to work, but I'm close to throwing in the towel. However, I've got a lot invested in it - the bike was cheap, the track was affordable but all the aftermarket work and parts have added up. Any help would be appreciated.


My heavily modded 03 Rm250 had a hell of a time with a slipping clutch. I actually wondered when you said you were going to use a Rm250 how the clutch would do. When I used to race that thing until I managed my clutch issues I would burn through at least a couple of clutches a season.
I see you already got a new basket. Another key if you can still find one is to get a hinson pressure plate. The stock one flexes. You can also drill some oiling holes on a new oem inner hub, if you don't want to fork out or can't find a hinson one.
Clutch plates are key, you say you got oem. I never ran them but as far as aftermarket goes the only ones that worked for me were wiseco.
Springs you can go aftermarket stiff or you could add some preload with some washers.
Run ATF type F for good clutch grab.
Power valves on a RM always puke goo so just route your lines accordingly. Moisture makes it look extra ugly.
Pretty easy to just pull the head and see what is going on in there. Do you know how to use solder to measure squish band?
 

tribalbc

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Before you go chasing down your clutch though it's pretty easy to know if it's slipping. Does your oil stink when you change it? The smell of burnt clutch is pretty obvious. I am in the habit of smelling mine on every change.
 
May 26, 2020
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All good points Tribalbc, thanks! I now remember seeing that you have an '03 RM. Interesting about the clutches in general. I'll look into a Hinson clutch plate, but I'm not sure what stinky clutch slipping oil smells like. My friend said the friction plates will be black vs brown/grey if they're spent.

As far as the solder squish - I've hear of that before. I could read up on it again, but I understand the concept: remove the plug, slip in a bent piece of solder, gently cycle the piston so that at TDC it compresses the solder to expose what the squish height is...?

Any idea on the track issues and the secondary chain / drive shaft being out of round?
 

tribalbc

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All good points Tribalbc, thanks! I now remember seeing that you have an '03 RM. Interesting about the clutches in general. I'll look into a Hinson clutch plate, but I'm not sure what stinky clutch slipping oil smells like. My friend said the friction plates will be black vs brown/grey if they're spent.

As far as the solder squish - I've hear of that before. I could read up on it again, but I understand the concept: remove the plug, slip in a bent piece of solder, gently cycle the piston so that at TDC it compresses the solder to expose what the squish height is...?

Any idea on the track issues and the secondary chain / drive shaft being out of round?

Burnt clutch just smells foul. If you are smelling anything besides the smell of regular oil this is probably what you are smelling.
You can do the solder the way you say but reliability this way is suspect at best. The proper way to do it is to remove the head, put a piece of solder across the entire top of the piston with contact on both sides. Install head and gasket, retorque and cycle through with hand on flywheel. I can get you a photo of what the solder shape that goes in later if you want. You really should pull the head anyways for a piece of mind.
As far as track goes I would be looking at alignment and bearings. Is it that out that you just can't run it a little looser? Sprockets out of round cause this to but the sprockets are too small to make much difference.
Easy way to date your cylinder. 01-02 have an exhaust bridge. 03 on open oval exhaust port.
 

wwillf01

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The lectron rod spec is for the big bore? Does the sputter happen when you are a good bit higher in altitude then where you start? Does it idle when you stop? If you don’t have a way to see exhaust temps are you doing a long pull and then checking the plug. If the power jet is rich then it will sputter at high rpms.... but you want to make sure your rich so you don’t toast the top end leaning it out. Now on the flip side it could be a lean sputter but they normally come rich out of the box?


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Nov 3, 2018
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My brother had a ktm 300 that would get water in the carb if his air intake ingested any snow. The bike would run poorly until the water was removed from the carb float bowl. It would cause no starts and poor running. He had to drain his carb constantly throughout a ride. Also it may be possible that the secondary chain is stretched causing inconsistent chain tension. It's been my experience that chains dont stretch evenly, and generally, service manuals instruct you to find the tightest point in the chain and set the free play at that point. I'm not suggesting that the driveshaft isn't bent, but I would try the easiest thing first
 
May 26, 2020
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The lectron rod spec is for the big bore? Does the sputter happen when you are a good bit higher in altitude then where you start? Does it idle when you stop? If you don’t have a way to see exhaust temps are you doing a long pull and then checking the plug. If the power jet is rich then it will sputter at high rpms.... but you want to make sure your rich so you don’t toast the top end leaning it out. Now on the flip side it could be a lean sputter but they normally come rich out of the box?


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I'll have to look at the email correspondence with Lectron but I know I told them what I was building. I think it's running a tad rich, as I'm blowing some premix on the tunnel and fender.

My brother had a ktm 300 that would get water in the carb if his air intake ingested any snow. The bike would run poorly until the water was removed from the carb float bowl. It would cause no starts and poor running. He had to drain his carb constantly throughout a ride. Also it may be possible that the secondary chain is stretched causing inconsistent chain tension. It's been my experience that chains dont stretch evenly, and generally, service manuals instruct you to find the tightest point in the chain and set the free play at that point. I'm not suggesting that the driveshaft isn't bent, but I would try the easiest thing first

Great insight. Thank you.

Before you go chasing down your clutch though it's pretty easy to know if it's slipping. Does your oil stink when you change it? The smell of burnt clutch is pretty obvious. I am in the habit of smelling mine on every change.

Clutch and oil inspection next.
 

wwillf01

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If you’re blowing oil like that out of your exhaust I would say you’re definitely on the Rich side for a Lectron I would lean out the power jet which is turning to the right a quarter to a half turn at a time. Ours can be totally encased in snow and it still works fine. The only problem if it gets really cold is the throttle sticking and that’s why we use a jacket.


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CATSLEDMAN1

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Comedy of errors, I understand, can't quite put a lid on anything. Couple of thoughsts.

1. Lectons often have sticky needle and seats, been an issue for 30 years, so before you kick your self to death make sure gas is flowing into the float bowl. I have run Lectrons on my bikes for 30 years, great carbs, but its good to know their quirks.

2. No Lectron out of the box is jetted perfectly, often adequate, with your mods etc etc. tuning that carb to run correctly is going to be importand, only blind luck would nail the jettting.

3. Lectrons don't have chokes, they have an enrichening circuit for cold starts, and it doesn't feed as much gas as the old Mikuni enrichenings circuits, so cold July morning at high elevation on my KTM200.......nada. ON the snow bikes I install primer bulb button in a convienent spot, you can't find the choke under engine covers anyway and even with a stuck closed float needle it fires one kick and the vibration will set the float needle loose.

4. Gearing, you need to check your track run out, forget all the sprocket sizes and calculator punching, track run out around 13.5 on a 250 in the snow is probably as high as you could go.

5. I spent most of last Sat. out in perfectly great new snow conditions helping and encouraging a young guy that put together a new to him $1500 two stroke snow bike. We never got 3 miles from the truck. He put together the last year of Yam250 2 stroke WR, basket case, maybe a 1998 ?, man is it raggy, but in budget, on a 2014 TS 120 kit. Some coolant leaks.......fixed and identified, 190 thermostat.......removed not good, plugged air cleaner air box, opened and make workable with a leatherman, heated bars that worked, non stock carb Keihin, removed at noon after run back to town for old MIkuni, up and down the road, fixed a loose wire that kept killing the whole thing. At end of day it shitz and gets, dropped needle and now holds mid range power, went up in main...way better. 13.4" track runout, we abused it by days end, four other experienced snow bikers checking in with help and advice but thats about what it takes to get these projects close to running.
 

mumur

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They are all custom but you're definitely getting a pretty short end of the stick right now. In general it seems like old tracks still work fine, so I feel bad it seems like you got screwed there. In my experience the newer bikes make a big difference to how much fiddling is involved (EFI on 4, other injection on newer 2strokes, electric start, etc) just really cut down on the random bullshit. Unfortunately don't have helpful tips like these other folks, just trying to help level set. My 2012 Beta was carbed and I felt like every time I went out I had some new problem that may or may not have ended the ride. Even when I felt like I finally had it dialed it detonated on me. After the initial (way less) tinkering with my 0 hour 2019 Honda, it has been pretty much flawless all season, just oil changes and valve clearance checking.
 
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Thanks mumer. I'm hoping to get this set up working, but will most likely buy a new set up in the future.

I got further with the project today. I was able to free the stuck bolts on the track. The issue I was having with the track not spinning freely was simply a spent secondary chain. It had a seized link or two. I replaced the secondary chain and tensioned it. Then I was able to eliminate the half link on the primary chain and tension it separately.

Next I started it up - maybe 5-6 kicks - and warmed up up before draining the oil. Like tribalbc said, it was pretty stinky and on the milky grey side of things. When I get a chance I'll open the clutch up and inspect the friction plates. I'm guessing they'll need replacing and I'll add an aftermarket pressure plate.

If I'm getting water in the intake I may have to change my velocity stack set up to more of a cylinder design.
 

wwillf01

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Water in clutch I would make sure the O ring on the oil fill is sealing . If the chain was that bad you could be causing a lot of extra stress on the clutch. Over the years changing the o ring has fixed that issue twice.. also making sure the bike gets warm enough to burn off water..


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tribalbc

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Thanks mumer. I'm hoping to get this set up working, but will most likely buy a new set up in the future.

I got further with the project today. I was able to free the stuck bolts on the track. The issue I was having with the track not spinning freely was simply a spent secondary chain. It had a seized link or two. I replaced the secondary chain and tensioned it. Then I was able to eliminate the half link on the primary chain and tension it separately.

Next I started it up - maybe 5-6 kicks - and warmed up up before draining the oil. Like tribalbc said, it was pretty stinky and on the milky grey side of things. When I get a chance I'll open the clutch up and inspect the friction plates. I'm guessing they'll need replacing and I'll add an aftermarket pressure plate.

If I'm getting water in the intake I may have to change my velocity stack set up to more of a cylinder design.


The milky color can be from lots of aluminum flecks from your clutch plates if the clutch is slipping too. Did you notice lots of aluminum flecks in the bottom of your oil drain pan?
 
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