It's not that all I want is top speed, I just want to be able to go anywhere...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.
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.
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?
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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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
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.
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.