CR 125 40lbs of compression--Big-Bore Kit time????

[Bamm Bamm]

So I bought a 97 Cr 125 about a month ago.. It was a basket case, paid $475 has a motor in pieces and almost everything else missing a silencer, but it had a pro circuit pipe.

So I went through put the motor back together the kid I bought it from said it had a new piston/ring in it(from the looks it did) and I finished everything tons of little odds and ends(replaced, 1 radiator, water pump, bearing etc.etc.etc.) Finally get it all together yesterday and go to try and fire it up and nothing.. man this thing has less compression than my 125cc 4stroke pitbike and 1000x less than my yz250..... Can't find my compression tester so I go to my buddies and it was averaging between 30-40psi... OUCH.... SO looks like the piston is pretty sloppy I'm about positive it will need to be sleeved or bored and I'm looking at my options.. I'm only about $800 into the bike... I'm really considering boring it to a 144cc I believe it was 0r a 149cc..

I'm wondering is it really worth the money?Will it be a noticable difference? Will I be able to keep up with my 250? I'm 6' 200lbs.... And also of course where would you guys recomend having the work done I want to get it started right away... Are there any dowsides to a big bore kit also??

Thanks
Dan

 

[robwbright]

You may or may not be able to bore it to 144 - apparently some of the CR's have a thin cylinder which prevents them from being bored to more than 134 or 139.

You will notice the difference regardless of whether its 134, 139 or 144. Apparently all 3 kits get near the same peak HP, but the 144 has more midrange and the 134 is more of a top end motor.

What do you mean by "keep up" with your 250? Speed is 95% rider, so YOU control how fast it's going on the track.

What you'll find is that a stock 125 is about 30-33 HP. Stock 250 2 strokes run in the mid 40s HP. A 144 that's been ported, high compression head for race gas, etc . . . will be in the 37-39 HP range. The best one I've seen on here was 39.6 HP on the dyno.

Given the weight difference between the 125 and the 250, a 144 is very quick, but it won't have nearly the low/mid of a 250.

Eric Gorr did my motor and I couldn't be happier with it. Depending on how much you like to rev it, you may find that you need to do top ends more often, but I haven't noticed much difference. Eric can give you the lowdown on all that.
http://www.ericgorr.com (site closed as he has it rebuilt). His phone number is floating around all over here if you run a search.

There is apparently very little extra stress on the motor resulting from the increased piston size because Eric's piston (which he designed for Wiseco) is only 1/2 ounce heavier than the stock 125 piston.

Try this link for my initial impressions after getting the motor dialed in:

http://www.dirtrider.net/forums3/showthread.php?t=126800

Most would say you're too heavy for a 125/134/144. However, read the last two posts in this thread:

http://www.dirtrider.net/forums3/showthread.php?t=124938

bclapham was racing at very hilly Glen Helen at 200+lbs and he liked the RM144 a lot. I'm sure others of that size would prefer a 450 4 stroke or maybe that new KTM 950. ;)

 

[Bamm Bamm]

Right on thanks so much for all the great info. I just noticed on his site that it says he's moving.. Is he still doing cylinder work right now then or would I have to wait a few months..I'm hoping I can dissasemble the motor tonight and send out tommorow


(I'm planning on buying 450 in a few months just not letting the wife know yet)...I have a inheritance I'm getting that I haven't told her about

 

[Bamm Bamm]

Hmmm. seems not to answer the number in another thread.. Is there any other place that does good work for this stuff?

I'm thinking he might be overseas or something from what I read in another thread

 

[robwbright]

From this thread:

http://www.dirtrider.net/forums3/newreply.php?do=newreply&p=1086629

Eric is still doing 144 kits with US Chrome. He has pistons and full kits in stock and ready to ship for the popular models.

He'll have details on his website soon, but if you want one now you can call him at 630-825-5645 or email him at :
ericgorr @ hotmail.com
(don't forget to remove the spaces around the @ sign)

 

[robwbright]

BTW, Eric is easiest to reach first thing in the morning.

 

[Bamm Bamm]

Sweeet thanks so much I'll try him tommorow mornng first thing

 

[chevy383cid]

If Eric is cover up you can send it to Kustom Kraft,they have a 12 day turn around , They are a good company that does quality work!! Done two for me in the last two years!!

 

[Bamm Bamm]

I was actually just checking out their website there prices are abit less also I noticed.... Hmmmm... thanks for the info,,

What do you have the 383 in???

 

[chevy383cid]

80 drag camaro-10:23 ET

 

[robwbright]

I was actually just checking out their website there prices are abit less also I noticed.... Hmmmm... thanks for the info,,

What do you have the 383 in???

Does their price include the porting, head work, piston and ring kit, case mods?

Just asking - I don't know. . .

 

[chevy383cid]

Last year I payed 265.00 for a big bore 134cc(on a 98 yz125)The work that was done was-bore,renikacil,hone,port to larger bore, modify power valve,new wisco piston, rings,pin,shipping ,The 134 did not require case modifications.

 

[chevy383cid]

Oh yea, they modified my head also.

 

[robwbright]

Wow. That's a good deal.