Any one try this setup for the yz 250
Esr 345 big bore
- Thread starter JammerMan
- Start date
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portgrinder
Well-known member
no experience on that one, but ive seen a few other bigger name kits that didnt do very much. i wouldnt be too pumped on the steel liner. it does look like they really tried to get a better exhaust setup though.
what i do remember from when we played around though is that the pc 2 pipe adds 4 through the whole rev range. cutting the head is a good gain too. i'de have to look back but i think we took 25 thousands off and that picked up another 2 over the whole rev range. Boysens rad really smartens up the low end.
what i do remember from when we played around though is that the pc 2 pipe adds 4 through the whole rev range. cutting the head is a good gain too. i'de have to look back but i think we took 25 thousands off and that picked up another 2 over the whole rev range. Boysens rad really smartens up the low end.
from motor building experience i've never found steel sleeved cylinders to work that well. You just can't get the velocity necessary in the transfer ports at higher rpms. They can make great torque and mid range, but just can't flow on top. might be good for torque woods bike with lots of mid range hit, but not a snow bike application.
I'm no 2-stroke guru though... Just my own experience.
I'm no 2-stroke guru though... Just my own experience.
Are you running a sleeve that wasn't port matched?
I've seen the whole steel liner debate over on tt and I really don't get it. Who cares if it's steel. The liner in the aluminum block in your car runs steel liners and doesn't wear out. I know it's apples and oranges but if I do wreck a piston and score the cylinder they offer a few oversizes and with one stop by my local machine shop and 2 20 dollar bills I can be bored and honed to the next size.
I have been looking and drooling at the ers345 with visions of mounting my st to it. About the only thing that worries me is I won't be able to carry enough gas.
I have been looking and drooling at the ers345 with visions of mounting my st to it. About the only thing that worries me is I won't be able to carry enough gas.
Seems like if set up properly they would make a great improvement to 250s. Anyone have any experience with rebuilding the top ends? Are replacement over sized pistons considerably more expensive then stock 250 pistons?
On a bore that big on a 250 case transfer port size is limited to the point where you can not get enough flow for top end power or should I say RPM.
Based on the fact that most big bore options for 250cc two strokes are below 300 cc I would venture a guess that that is the magic line for torque without the loss of to much top end.
Snow bikes need over rev to work well.
Eric makes a great big bore in that displacement may want to talk to the man directly .
Based on the fact that most big bore options for 250cc two strokes are below 300 cc I would venture a guess that that is the magic line for torque without the loss of to much top end.
Snow bikes need over rev to work well.
Eric makes a great big bore in that displacement may want to talk to the man directly .
I've been wondering about the 345 too. Was looking at a CR500 conversion and even picked up a newer AF for the conversion but I'm not sure I want to tackle that project anymore. The few 345 reviews have people raving about the power over the smaller bore kits. As mentioned TT has a lot of info on this and the steel insert debate which doesn't worry me much. Would like some real world feedback on this bore kit on a snow bike though.
chrome it and it wil go faster
internal combustion engines are cooled when combustion chamber heat flows out through the piston crown via the rings and absorbed by the cylinder wall and then carried away by coolant or air.
As you make more hp it requires more combustion chamber heat, so as engine make more hp, the piston crown and rings and cylinder walls have to operate as peak efficiency.
Steel tranfers heat slowly.......so steel pistons went away 60 years ago replaced by better heat transferring aluminum pistons.
By the early 70's performance engines needed aluminum cylinders to get rid of heat created by bigger HP numbers, so we had chromed aluminum cylinders, but the chrome was soft and flaked. Kawasaki helped pioneer NICISIL they called it electro fusion bore. Now your 125 could scream at razor lean jetting and not seize if you had your chit together. Aluminum piston flowing heat to aluminum cylinder.
So now you want to go back to slower piston/ring heat transfer with a steel liner. No big deal. Just keep your engine comfortablely fat so it runs cooler. Find some rings made to run on a steel surface ? Knock down the hp and rpm should be ok.............like we were in the 60's.
So unless hp and safety are a concern, steel liners are fine.
internal combustion engines are cooled when combustion chamber heat flows out through the piston crown via the rings and absorbed by the cylinder wall and then carried away by coolant or air.
As you make more hp it requires more combustion chamber heat, so as engine make more hp, the piston crown and rings and cylinder walls have to operate as peak efficiency.
Steel tranfers heat slowly.......so steel pistons went away 60 years ago replaced by better heat transferring aluminum pistons.
By the early 70's performance engines needed aluminum cylinders to get rid of heat created by bigger HP numbers, so we had chromed aluminum cylinders, but the chrome was soft and flaked. Kawasaki helped pioneer NICISIL they called it electro fusion bore. Now your 125 could scream at razor lean jetting and not seize if you had your chit together. Aluminum piston flowing heat to aluminum cylinder.
So now you want to go back to slower piston/ring heat transfer with a steel liner. No big deal. Just keep your engine comfortablely fat so it runs cooler. Find some rings made to run on a steel surface ? Knock down the hp and rpm should be ok.............like we were in the 60's.
So unless hp and safety are a concern, steel liners are fine.
I know there was someone in here that ran a 300 kit and was having issues with long term reliability once he tore it down it did not look good ..
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