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03 CR85 Help!!

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Hey guys i bought my girl a 2003 cr85 two years back, and its always ran and started good but Ive noticed that there is literally no bottom and mid range power. When it hits high end it screams like crazy and is super fast. But is boggy low end and mid.... Any suggestions? she starts first kick an has never gave me any problems. My wife loves it but i know there should be more power down low, even on a 85. Thanks guys she will appreciate it! BTW ive never touched the motor, it is girl ridden. haha

Edited by smallz700r

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If you've had this bike for 2 years and haven't refurbished the top end....it's very likely past due.

Motocross track ridden, 20 hours of use is pretty much the limit to maintain best performance and reliability.

Edited by mlatour

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Yeah I usually do top end in my 250 every winter, but her 85 has lots of compression left and starts first kick idles good and everything. She literally just putz around the yard slowly or down some trails up north. It's very easy ridden I just don't know why there is no low to mid power?

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Compression that 'seems fine' at the kickstart lever doesn't mean much.

Pull the exhaust off, look up at the piston thru the port.

If you see dark discoloration on the piston under the ring, that's combustion blow-by = worn = loss of performance

 

These are race engines, even when used recreationally they still need to be refreshed on a regular basis to prevent loss of driveability. 

Edited by mlatour
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The 03-07 Honda CR85's had a mid top porting and didn't have as much low end as the earlier model CR80's.  It is tough to tell if the bike has no low end because of a mechanical problem or if you are just noticing that the bike has no low end because that is the way honda designed it.  Refreshing the top end is never a bad idea though especially if it has never been done.  If you want to keep the 2 stroke but want more low end and don't mind spending a little money on it, getting a 105cc big bore kit with a low/mid porting job along with a 10oz flywheel weight and you will be shocked at how much low end the bike will have.

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Before ordering a piston kit,

first dis-assemble and measure the cylinder and old piston, see what you have in there now.

Installing a new piston in a worn out cylinder won't help much or, for very long.

Edited by mlatour
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20 hours ago, smallz700r said:

thanks guys, I guess I will put piston and rings in her for the hell of it, any suggestions on what pistons run the best in the 85? 

I always put wiseco's in my 80's.  Mine has a 52mm piston in it though (105cc).  OEM is always the best option and cheapest sometimes as well.  I usually pick the cheaper between OEM and wiseco on all my 2 strokes. 

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As reference I just picked up an 06 85cc for my son low miles on piston. The standard jetting works great for us at 2200 ft. 32:1 mix crisp throttle and no splooge so check your needle position and that may help. Sounds like the main jet is correct. Our bike gets up into the power band range quick without a power valve and doesn't bog before that but not a lot of power in the low range. I would say it has about 25% that of the power band at low range but that seems normal to me for a non power valve two stroke. I try to ride just short or on the pipe and work the clutch. Manual says stock bike is for up to a 150 lb person but it will lift the tire with me on it when I hit the power band. Rode it again last night and as you said it's not a put around bike but in mid and high range it screams.

Edited by knd roy

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