CR250R cylinder

[QuentinCR250]

Hi all, I am after a bit of advice regarding the cylinder on my 2001 CR250R, in the weekend I had the unfortunate incident of the power valve clipping the piston rings and doing some damage, after stripping the top end down I found the cylinder has at some stage been fitted with a steel sleeve, now there is a bit of damage from the broken piston ring and I am wondering the best path to take. Are steel sleeves a good idea in bikes such as this? or instead of repairing the sleeve should I try and source a new cylinder for the CR? any ideas or advice appreciated.

 

[steve.emma]

hi there,
steel sleeves may not make for the best power.. but at least you can re-bore them unlike a chrome bore.
if there is damage to your cylinder bore why not just get it bored oversize and order a aftermarket piston kit like pro-x or wiseco.
i did this on my yz250 (factory steel sleeve) and its now 1.25mm oversize and ordered the piston from mx-south,now it rides like a new one.

steve.

 

[QuentinCR250]

Thanks for that, Yeah might be the best option especially with regard to saving money. Does anyone know how long steel bores last before they need attention, ie if I get it honed or rebored, and fit a new piston, how many hours would you expect to get before a re bore... thanks

 

[steve.emma]

hmm i dont know how long they last before needing a rebore again... im guessing nowhere near as long as a chrome bore as the steel is so much softer and it wears oval. BUT if your bike has a aftermarket steel sleeve then those are usually very thick and can take many rebores (normally .25mm minium at a time) before they would be scrap, it would last longer than you would own the bike im sure.
steve.

 

[steve.emma]

i see you are also from NZ so for your intrest the place in Tauranga where i live that did the rebore for my bike only charged $80 to go from a .75 to 1.25mm o/s so its not very expensive to do.....its the pistons that cost.....

 

[QuentinCR250]

Thanks Steve, interesting reading I have only had the CR a couple of weeks, and was perfectly happy with if before the problem so If I can get it fixed with the steel bore with little expense that would be great. Another thing I was unsure about was the piston ring clearence, having a steel liner means I will not be able to set the ring gap to that as stated in the manual I assume or I am likely to suffer a cold seizure? Do you have to set the gap much bigger to allow for the expansion of the different metals???

 

[steve.emma]

good question about the ring gap i dont really know the answer to that one... my cylinder has a factory steel sleeve so i just followed the manuals specs. i would think that as long as you dont have the gap set on the small side of the specs then it wouldnt really matter but if i was you i wouldnt want to risk it either by not knowing.... maybe someone else will answer this one...

 

[CR3999]

Buy a 99 jug for it you will like the power alot better. The 99 has a nice low-in and is a blast to ride.