Other CRF100 or XR100 in CR85 frame

anyone done this project? we've had a CRF100 for quite a while and I'm looking to do some upgrades. we currently have a set of CR85 forks, a cradle, FMF power core 4 and a BBR120 kit on it. I've just sent the head and carb out to our favorite mod engine builder and I'm going to take the flywheel off and lighten it up. I also just bought a CR85 donor bike to drop the engine into for a winter time project.
so now for a couple of questions. I'm also looking at adding the Takegawa Heavy Duty 5-disk clutch, is it worth it? Is there a weight that works best on the flywheel or just shave it down as low as I can go? what kind of gearing are most of you running, we still have stock and just don't use first gear. is there one way better to fab the lower mount in the 85 frame than another and is there anywhere to go to get some good pictures? I know we're not going to have anywhere near the power of the 140/150's but is there anything I'm missing to get the most out of it without going to the high dollar big bores and head? I've did a few searches on here and other sites figuring I could get some solid frame info but I really haven't came across much so any advice would be appreciated.
 
FUN, wringing out a pitbike is a blast. I'm just wanting to have more of a blast. the stock CRF100 rear suspension is what holds you back the most, hence the CR85 chassis. the motor is a little weak for hauling a grown man around and the 120 kit helped so I'm just adding a little extra HP to increase the fun factor a little more. I don't have any money to blow, but you can't take it with you either so...just as well have FUN!
 
I am kind of a why ask why sort. years back we put the suspension off of a leading axle cr80 on one, very nice result. I would like an xr200 motor in an 85 frame. there are some good big bore kits with a complete cylinder available for that(the xr 100) one. money and practicallity on dirbikes are kind of mutually exclusive anyway.
 
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haha, I hear you. we have a local race that's called the "Pitbike Des Nations" it's 3 team members but you only do one moto each. rules are anything 150cc and under, 19 front 16 rear tires. this year they plan to have a plus age class hence the mods for my fat arse lol. after the racing there's lots of BS'ing, beer drinking and a band. Sounds like a perfectly good reason to mod the pitbike to me. last year there were 18 teams that signed up and my son and two of his buddies got 2nd overall, everyone that beat them were riding CRF150's or TTR125's. I know we won't be getting to there HP levels but our team doesn't need but a little extra HP and the suspension will make up the difference I hope. I have looked at the full mod head/cylinder big bore but damn...I don't think I want to spend that kind of cash. our engine builder is very good, I have complete confidence he will get us all the little 100 can put out with dropping the really big bucks.
 

SRAD97750

Moderator
Staff member
Pitbikes are a real rippin' riot. I would like to see more if you end up performing this or any modifications! -BIG DAN:thumb:
 
I need to get back on building the bigbore 85's I have sitting here. Not exactly the same. But I am thinking 20 somewhat useable ponies in 170 lb rigs ought to be fun on trails and m backyard course.
 
Pitbikes are a real rippin' riot. I would like to see more if you end up performing this or any modifications! -BIG DAN:thumb:

I will post some pics as I go along. hoping to start later this week. the 85 was only a small wheel so I bought a longer swingarm off ebay and we get a pretty good deal thru Excel so a new 16" rear rim and spokes are also on the way. stopped by our suspension guys place last night and talked to him about what springs I wanted and that we will have to get our current forks back up to stock height after shortening them for the CRF100. would really like to hear some opinions on the Takegawa clutch but I'm probably going to order it with the extra HP I doubt the stocker will last long.
 
I will post some pics as I go along. hoping to start later this week. the 85 was only a small wheel so I bought a longer swingarm off ebay and we get a pretty good deal thru Excel so a new 16" rear rim and spokes are also on the way. stopped by our suspension guys place last night and talked to him about what springs I wanted and that we will have to get our current forks back up to stock height after shortening them for the CRF100. would really like to hear some opinions on the Takegawa clutch but I'm probably going to order it with the extra HP I doubt the stocker will last long.


We run our TTRs fairly stock with only minor mods. Even then it's just stiffer springs and aftermarket levers and stuff. One of our buddies has the BBR TTR frame package which is basicly a ttr125 motor in a big wheel 150 frame. The seat sits about 6" higher than a regular ttr125l frame so it's almost at big bike hieght. Fun to ride but it just kills us when it comes to full MX racing.
 
We run our TTRs fairly stock with only minor mods. Even then it's just stiffer springs and aftermarket levers and stuff. One of our buddies has the BBR TTR frame package which is basicly a ttr125 motor in a big wheel 150 frame. The seat sits about 6" higher than a regular ttr125l frame so it's almost at big bike hieght. Fun to ride but it just kills us when it comes to full MX racing.

I understand that, the guys that put on the PBDN also ride every Monday and they all have some pretty sweet rides. most are the TTR's with the big wheels and motors that they have to push start. there are a couple that have the CRF150 and one or two that have the KLX140 also. after running against these guys you can see why I'm trying to make a few mods lol.
 
I understand that, the guys that put on the PBDN also ride every Monday and they all have some pretty sweet rides. most are the TTR's with the big wheels and motors that they have to push start. there are a couple that have the CRF150 and one or two that have the KLX140 also. after running against these guys you can see why I'm trying to make a few mods lol.

The 140 and 150 are fast out of the box when compared to th 7hp TTR. Lol
It makes me wonder why they just don't run actual race bikes at this point. :smirk:
 
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