120 tire on RM 250

[Crash 142]

I have done a search and cannot find this answered - will a 120 rear tire (a 756) fit on my 2004 RM 250? It seems the chain might rub on the edge knobs. I'd love to hear from someone that has put the 756 120 on this exact bike.

Also, anyone want to offer an opionion on a 120 for a 250 two stroke? I'm looking to decrease wheelspin. I'm also hoping the bigger tire will slow the revs a bit (yes, I already have a fww - a 10 oz., and I dropped one tooth on the rear sprocket). I ride MX only, and want to tame down the power hit and stop spinning the rear tire so much.

Thanks.

 

[bclapham]

i would look into the bridgestone 401A/402A that comes stock on the RMZ450. they are that bit wider.

 

[christopher in tam]

If a larger tire would decrease wheel spin then the factory teams would be using 250cc size tires on thier 125's.

The rear tire needs to be able to dig alittle to get down under the top soil where the ground is harder and tackier. The wider the tire the harder it is for the tire to get down to this tackier part. On a cr500 with its really wide rear tire this is not a problem because it will burst away the top soil and get that big tire down into the meat of the dirt with its mightly torque. The smaller the engine the skinnier the rear tire should be so that it can reach that certain deepness in the ground with the power thats provided.

Also look at this... when you are on the gas your rear tire is basicly digging (and reaching for traction). After it digs down to the traction and the bike starts moving forward then it will need to displace the dirt infront of the rear tire to move forward while maintaining traction, the wider the tire the more dirt that will need to be displaced, the more power is wasted displacing dirt.

Basicly, the larger 120 tire on your 250 will rob power and provide no traction increase.

 

[Rcannon]

I tried a 120 series 756 on my yz 250. It did not rub.

I did not like the tire. It had a heavy feel to it. The traction was not much different than a regular size tire.


There was no way it would substitute for a flywheel weight.

 

[2-Strokes 4-ever]

I'll make this short, I have 2 broken wrists... Run a 110, spend $17 on a YZ250 reed spacer (and 5 mm longer bolts) Works like magic to broaden RM's power and make that drastic hit more tolerable. (a.k.a. power to the ground) My 12 oz. flywheel weight was NOT enough.

 

[Danger]

I'll make this short, I have 2 broken wrists... Run a 110, spend $17 on a YZ250 reed spacer (and 5 mm longer bolts) Works like magic to broaden RM's power and make that drastic hit more tolerable. (a.k.a. power to the ground) My 12 oz. flywheel weight was NOT enough.

Did you replace the manifold as well? I read someone did, but the only reason I can think to do that is to keep the carb 5mm further forward in the stock position. I have the spacer already but have not fitted it. Any clearance problems with the stock manifold?

 

[2-Strokes 4-ever]

It will bolt right up with all stock parts. When you move carb. or exhaust away from cylinder it broadens power...on any bike. Spacer against cyl....reed cage...manifold...carb. Adding 2-3 exhaust washers into exhaust flange before pipe will give similar results (with some sacrifice of top-end power.) A V-Force reed assembly helps too.