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CR85R Expert modifications to make it a good learner bike

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Hi everyone - noob dad here (at least from a dirt bike perspective). I have told my kids (10yo son and 12yo daughter) that I would get them a dirt bike and give them a chance to do some racing, if they like it (there's a flat track site/weekend series within a couple of hours from where we live that looks like fun). We'll probably also take them to a motocross track nearby to learn on and see how it goes. They love riding on our street motorcycles, but have never ridden dirt bikes before.

 

I got a great deal on a fully race-built CR85R Expert that I know is too much bike for them to begin with. What I'd like to know from the experts here is what the best way is to go to help them learn. I am thinking about getting smaller wheels & tires, maybe lowering links (for now) and (hopefully) a stock CR85 (or smaller) motor that I could install for them to learn on before riding the full-on race-ready setup that is on it now. I shouldn't have any trouble working from the manual to swap out the engine or take care of the bike, but the challenge will be finding sources/suppliers in southern Ontario (Durham region). I have a shipping depot service that I can use in the US, if that's the recommended way to go.

 

Hopefully you guys can point me in the right direction and help build a plan of attack. Who knows, you guys may tell me that I made a huge mistake and should sell this bike and buy them something else.

 

Thanks in advance for the help!

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Flywheel weight and a bigger rear sprocket will help in avoiding stalling a high-revving / low torque 85.

 

How tall are your kids?

 

At that age they're still growing fast, investing in expensive lowering mods/small wheels could quickly become un-necessary.

 

Depending on their height, if they can tippy toe somewhat confidently on the present height of the bike,

get them used to having a high bike, when the time comes they might progress easier into riding a full sized bike.

Edited by mlatour

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Thanks for the responses - I'm going from the information that the seller gave me. He told me that the motor was built by a local performance shop, so I'm not entirely certain (yet) what has been done to it - he told me that, as it sits right now, runs "race fuel" and would be competitive if ridden by an experienced rider. So I just don't have the details. If I can get them comfortable on a performance machine now, all the better (fewer bikes to buy and sell lol).

 

I'll get the kids to both sit on it when I get it home and see if they are tip-toe or better. I'm pretty sure my daughter will be. And yeah, they grow quick, so I don't want to make any big investments that will be unnecessary by the time the summer rolls around.

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make sure you stress throttle respect, if it is a race motor that thing will get them in trouble real quick (not that a normal 85 wouldn't).

 

you might be wise to get a fairly low power bike till they learn clutch and basic mx skills.

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My son learned on a pw80 and then a kx100. He did not do particularly well. The hit was never adjusted to so he always rode off the pipe.

He actually preferred it without the flywheel weight. While it smoothed the hit it also makes off idle soggier.

Put a machine washer in the pipe in the flange. Adjust size to power required. This works even better than disconnecting the pv. You'll need to drop the main alot.

Push the forks up in the clamps and take some preload off the rear. A little extra in the rear is good to slow the steering down.

Edited by seer

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Thanks for the info, seer. Good lord, though, I must have a lot to learn. I have no idea what most of your post actually means... I guess there's a whole new language that I need to learn for this sport.

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Sorry for language barrier. Try riding it around your yard and you'll get a better understanding.

Be careful. They wheelie quickly with an adult on board.

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My son learned on a pw80 and then a kx100. He did not do particularly well. The hit was never adjusted to so he always rode off the pipe.

He actually preferred it without the flywheel weight. While it smoothed the hit it also makes off idle soggier.

Put a machine washer in the pipe in the flange. Adjust size to power required. This works even better than disconnecting the pv. You'll need to drop the main alot.

Push the forks up in the clamps and take some preload off the rear. A little extra in the rear is good to slow the steering down.

 

I don't want to hijack this thread but I was considering doing some taming mods to a 2001 KX100.  Would you recommend doing the washer only and skipping out on the flywheel weight and the disconnecting of the power valve?

 

You said you had to lean the main jet when you added the washer?  Do you know what size you ended up with?  Did the washer have any negative effects on bottom end power?  Or did it just mellow out the hit?  Thanks for the info.

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Try the washer first. It's cheap and easy. Pull the pipe to measure and pick up some machine bushings to fit. If you have a decent store they'll have a few different id's available.

I remembered today I eventually ended up with a 3/8 or so aluminum insert. I shaped a venturi on the cylinder side. Better idk? Prettier though.

Sorry I don't remember what main jet. It depends on the restriction size. I'm thinking down 10 or so and was still rich.

It doesn't hurt lowend. I felt it helped right off idle a little. Only once the power valve opens will you notice.

You'll still have a less than perfect trail bike. On level ground it's ok but the first hill will still need some clutch skills.

If you ever get a chance try a ktm. The 85 has more bottom than the kx100. I haven't tried the 105.

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The CR85 is a poor learners bike. It doesn't have a powervalve, so the power delivery is peaky and aimed towards experienced riders.

 

Rather trying to transform the CR85 into something it's not, you would be better off selling/trading it for something more appropriate for your kids.

Edited by CamP

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