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yz300 woods / snowbike build

dirtrebel

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I would love to look at this bike I got a 15 yz250 I am thinking about converting.
I live in Great Falls but I come to bozeman. Is it still a 300 or back to a 250?

its back to a 300 again for snow. Ya pm me if u wanna check it out sometime.

I finally got a q07 rod for the smartcarb friday, so I will be installing that today and trying it again this week.
 

dirtrebel

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Tomk came out and we got a good ride in on new years day. He rode the smoker all day but I did take it for a rip. as of now I am running the q07 rod and having to have the clicker at 25-30 clicks out from full rich to keep egt from spiking on short and long pulls. Idles bad but helps richen the entire range so works for now. I will get the q05 coming so I can hopefully set the idle leaner and get the topend richer the right way. water temps runs between 120 and 160 with the pipe wrapped and no shielding. Air temp was between -10 and 20f. It is fun and eventually went everywhere the my yz450 longtack did, but it took alot of work in deep bottomless snow. I think I might have to go back to the stock pwk though if I can never get the smarty rich enough. It will be a fun bike for sure, but I think the 450 is really the go to ride. For me I would only do another 2 stroke if it was a 500cc. Here's a vid from when I rode it, just meadow cruising nothing too great, there's no lugging it, topend only! Took some getting used to after riding the big 450 all day!

https://www.youtube.com/watch?v=aZV2LhWfO-I

also here is one from earlier in the day on my 450, this was where the 300 smoker had a hard time, but eventually got it done.
https://www.youtube.com/watch?v=tV1PPPNt6qQ
 
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mxracer299

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Nov 24, 2010
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Glad you're getting closer! I ended up with a Q05 in my 300, the 40mm carbs are using Q07 or Q09, kind of wierd. Just wait though, there are some more issues we are finding, some of the needle and seats are wrong and they will randomly flood when shut off, turn of the gas when you turn the bike off. Starting when cold sucks, you can run a fuel primer or I got a 1oz Nalgene squirt bottle and I lift up the pre filter on the pod and give it a 2-3 second shot of fuel when cold, it fires immediately. Even with the carb heater the carb freezes, I wrapped mine with the 1/2" thick closed cell water pipe insulation that you can get at hardware stores. All of that being said, my bike is the fastest dirt bike I've ever ridden, it will wheelie at will anywhere, even in 3 ft of heavy powder, it is stupid fast. Keep playing with it and you'll eventually get the right combo. They are going to take a some tinkering because nobody has done them, but it will blow your mind when you get it right. If you dont have any mid, try putting in one step thinner base gasket, it will give you more low to mid, but you will loose a bit on top. Even then you dont lug around a 2 stroke much, they work well when they sound like a chainsaw! Haha Set your gearing so you can do your techy riding in 3rd gear pinned, if you're using second gear more than third you're loosing too much torque.
 

dirtrebel

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Glad you're getting closer! I ended up with a Q05 in my 300, the 40mm carbs are using Q07 or Q09, kind of wierd. Just wait though, there are some more issues we are finding, some of the needle and seats are wrong and they will randomly flood when shut off, turn of the gas when you turn the bike off. Starting when cold sucks, you can run a fuel primer or I got a 1oz Nalgene squirt bottle and I lift up the pre filter on the pod and give it a 2-3 second shot of fuel when cold, it fires immediately. Even with the carb heater the carb freezes, I wrapped mine with the 1/2" thick closed cell water pipe insulation that you can get at hardware stores. All of that being said, my bike is the fastest dirt bike I've ever ridden, it will wheelie at will anywhere, even in 3 ft of heavy powder, it is stupid fast. Keep playing with it and you'll eventually get the right combo. They are going to take a some tinkering because nobody has done them, but it will blow your mind when you get it right. If you dont have any mid, try putting in one step thinner base gasket, it will give you more low to mid, but you will loose a bit on top. Even then you dont lug around a 2 stroke much, they work well when they sound like a chainsaw! Haha Set your gearing so you can do your techy riding in 3rd gear pinned, if you're using second gear more than third you're loosing too much torque.

installed the primer a while back, works great for dead cold starts. right now its geared where 5th is barely fast enough for the trail, most techy riding is 2nd and even 1st, so could go down a touch but don't wanna lose too much speed on top. we had the flooding once but it turned out a pine needle was stuck in the inlet! I had the tank off for 3 weeks waiting on the rod I guess the pine needle fell in during that time. I did notice the slide sticking slightly a time or two but went away quick. I will keep tinkering. Somebody bought all the q05's lol so I am waiting again, will call monday, maybe they have them now. might try the thinner base gasket too, thanks for all the help!
 

Yrocmoto

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YZ gearing

You mention some case gearing above, what is your countershaft sprocket with that setup? The YZ comes stock with a 14 countershaft, but timbersled suggests a 13, so I put that on when I was setting my bike up. Went for my first ride today and could probably barley hit 25mph, that's just waaaayyy too slow and boring on the trail for me. Seemed fine boondocking in the powder though. 1st was useless.

I was thinking it would be easiest to go back to the 14 on the countershaft and throw an extra master link on the chain? Is this a bad idea? How hard is it to mess with the sprockets in the TS drive?? I'm really frustrated that it is so bad setup the way it came. I have a 2014 ST FYI.
 

dirtrebel

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You mention some case gearing above, what is your countershaft sprocket with that setup? The YZ comes stock with a 14 countershaft, but timbersled suggests a 13, so I put that on when I was setting my bike up. Went for my first ride today and could probably barley hit 25mph, that's just waaaayyy too slow and boring on the trail for me. Seemed fine boondocking in the powder though. 1st was useless.

I was thinking it would be easiest to go back to the 14 on the countershaft and throw an extra master link on the chain? Is this a bad idea? How hard is it to mess with the sprockets in the TS drive?? I'm really frustrated that it is so bad setup the way it came. I have a 2014 ST FYI.

yea on my first ride (post 27 above) I tried stock timbersled gearing (I am running the 13 countershaft) like you 5th was tapped at like 25 mph. Next I tried just reversing the chaincase gears (20 on top 17 on bottom) that was too tall for boondocking, it was fast on the trail. Now I am running 17 ton top and 16 on bottom in the case with one link shorter chain and rear 2 cover standoffs removed so chain does not rub them on decel. that is pretty good, but I think I will reverse that and put the 16 on top and 17 on bottom to gear it down a touch, and give that a try. 5th will be a touch slow but 1 thru 4 will be better for mountain riding. I would not run 2 master links if I was you, that will make the chain too long most likely because you cant just add 1 link to a chain, you always have to add 2 to make the chain go together right making it waaay longer than you would think. and also its just not the right way, just buy a new chain if you decide to go that route. you could maybe get away with a 14 countershaft to 16 jackshaft and leave the case alone, but in my experience the primary chain is so sensitive to length I usually leave it alone if the tension is good and then play with the gearing on the case side. These 5 speed close ratio 2 stroke race bikes can be made to work, but they are a pain and have to be ridden super aggresive! The gearing is super important and you will never get 60+mph on the trail and good mountain deep snow setup. shoot for like 45 on the trail and good deep snow performance, be ready to tinker alot! 4 strokes are pretty much gas and go and smile, and check valves a few times a year.
 
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dirtrebel

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so on the new years ride the q07 rod (38mm billet)was BARELY rich enough at 7500-9000 feet with the low speed adjuster super rich to help. I took it for a ditchbang in front of my house alongside the highway with the same settings as new years and it was waaaay lean here at 4850 feet. so if I get the q05 and that is still not rich enough then what? I dont usually ride that low, but what if I did, I thought that was the point of the smarty? I am going to try the stock carb immediatly and see, I am thinking the smarty is just not rich enough for this bike, maybe I need the 4omm for whatever reason? plus with the electronics for the ignition I have unhooked I am just thinking the smarty is not for the yamaha. The reason I have not tried the stock carb yet is because the heat collar did not fit it well at all so I will either have to wrap it with hose or make my own collar. so trying to stick with the smarty because of the heat. I will try the stock carb in the ditch without heat and if its way better find a good way to heat it up. any input is appreciated.
 

Yrocmoto

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Gearing

Thanks dirtrebel, I hope i don't have to tinker too much and don't regret going with the YZ (I was going to put it on my 525 with the wide ratio tranny), but so many going with 2 strokes I decided to go this route.

Are those TS case gears just countershaft sprockets? Can I get them from any parts place?
 

dirtrebel

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Thanks dirtrebel, I hope i don't have to tinker too much and don't regret going with the YZ (I was going to put it on my 525 with the wide ratio tranny), but so many going with 2 strokes I decided to go this route.

Are those TS case gears just countershaft sprockets? Can I get them from any parts place?

timbersled case gears come from timbersled or some of their dealers stock some sometimes, like 75 bucks. They are proprietary to timbersled. 25mm keyed shaft for 520 chain. 9miler on here makes some and also D.O.C out of canada makes some. you can try to just reverse the case gears it may be good for you for free. maybe order a fit kit for the 525 so u have it on hand to try it, lol. I would buy your 250 fit kit from you for spare parts for my bike if you ended up not liking the yz.
 
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dirtrebel

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just talked to apt, sounds like I should have gone with the 40mm. He said it pulls more air (12%) which I thought would make it leaner, but by pulling more air also pulls more fuel. He said most snowbikers are going with 40mm. He's gonna ask Corey about trading mine in on a 40mm. Stock carb and a handful of jets here we come in the meantime!
 

Yrocmoto

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Yeah, I"ll try flipping them first. Where do you think 20/20 would put me? Wanna sell me your extra 20? Also, looks like a 15 countershaft will fit on the YZ, maybe that will take up the slack of the longer chain and could be a good ratio??? For $9, I think I'll give that a try first too.
 

dirtrebel

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Yeah, I"ll try flipping them first. Where do you think 20/20 would put me? Wanna sell me your extra 20? Also, looks like a 15 countershaft will fit on the YZ, maybe that will take up the slack of the longer chain and could be a good ratio??? For $9, I think I'll give that a try first too.

20/20 is 1 to 1 which is right in the middle of the two ratios i'm working with now. 17 and 17 would be the same as 20 to 20. 17/16 is like 1.06 to 1 and 16/17 is around .94 to 1. the only downside to running 1 to 1 is that is all it will ever be you cant flip them to gear up or down a touch , however it might be the sweet spot. I guess the only downside to going 20 to 20 is you might need a longer chain? and that you only will have one ratio available, no flipping them for a 10% change. you could order an 18 and try 17 and 18 or you could get a 16 like me and try 17 and 16. lots of possibilities by just buying one sprocket. I think if I remember I wanted to go 17 to 17 but the stock chain was too long and if I removed a link it was too short, so I went with the 16 and 17 combo because it worked with a 1 link shortened chain. I think I better hold onto my 20 for now, I would have to charge you almost the same as a new one anyway. I guess in summation 16 and 17 is the only ratio I could get to easily work with an extra each 16 and 17 on hand to choose from at the time by just running a 1 link shorter chain.
 
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mxracer299

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Here's a really handy gear calculator, one you have a baseline it makes it easy to see what gears are going to give you for a final drive ratio. Another thing to remember is 14 kits run 8t driver, 15 kits run 7 tooth, hence the gearing change in the chaincase this year. http://www.nightrider.com/biketech/calc_gearratios.htm Here's a pic of gear ratios I calculated for my bike this year. And its usually 3t per link when figuring out if a chain will fit but it does get thrown off slightly when making diameter changes with the sprocket sizes.
 

dirtrebel

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nice gearing chart. I think 14 kits run 7 tooth drivers with 17 over 20 in the case. and 15's run 6 tooths with 17 over 17 in the case though. yrocmoto said he had a 14 kit so that was what I was going off for him.


I have a 2014 ST FYI.

Here's a really handy gear calculator, one you have a baseline it makes it easy to see what gears are going to give you for a final drive ratio. Another thing to remember is 14 kits run 8t driver, 15 kits run 7 tooth, hence the gearing change in the chaincase this year. http://www.nightrider.com/biketech/calc_gearratios.htm Here's a pic of gear ratios I calculated for my bike this year. And its usually 3t per link when figuring out if a chain will fit but it does get thrown off slightly when making diameter changes with the sprocket sizes.
 
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mxracer299

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My sx is a 6t, with 16-17 in the chaincase but it was too low. Im running 14-18-17-17 and it seems to be about right. I'm able to hold 3rd in techy stuff and have OK trail speed. 2 strokes just dont have the rpms for high trail speeds, kind of a bummer. We'll have to meet up at kings hill soon and do some comparisons on our bikes and see how they're doing, looks like 2ft new and there is very much avy terrain so it should be good with the current snow conditions.
 

Yrocmoto

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How in the f do I remove the case gears?!?! Been prying on them all morning. The top one is 3/4 off and the bottom one won't budge, bent 2 pry bars (crappy mild steel though).
 

dirtrebel

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right tool for the job

cheap 2 jaw gear puller from the auto parts store. if its a used kit the keys get pounded and makes removal a biotch. use anti seize on key and sprocket upon assembly and red loctite on the end of shaft bolt, tourque to max 70 ft lbs, don't use air to tighten the bolt can break, keep a good check on bolts and chain tension, every ride sometimes once during the ride till u get to know the kit.

puller.jpg
 
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dirtrebel

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just got rid of the smart carb. wow! around my yard its a whole new animal! accelerates wheelies jumps like never before! I'm sure its a good carb but on the yamaha it does not work due to the electronics that work off the throttle position sensor. Luckily the bike came with a jd jetting kit, so i went ahead and put in a pretty fat setup. It started first kick without primer, off course the plastic tee for the primer broke so I'm hoping I wont need that dumb thing anymore. The heat collar is a less than ideal fit on the throat of the carb due to the shape of the floatbowl, but it seems to work for now, I can make a new one if need be. I'm not gonna post my smarty for sale till summitboy sells his but if anybody reads this and is a local southwest montana person and wants it pm me. I hear it works on ktm 300's and big 500 smokers that don't have carb-ignition electronics.
 
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