92cc in 85 mod class?

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#1
Can you legally run a 92cc in the 85 mod class. If not, what can you do to the engine besides a port & polish, V-force pipe. Help!!
 

elf

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#3
Try some vp ultimate 2, get it jetted to perfection and remember its 95% rider and 5% bike.
 
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#4
Thanks guys,

I'm not trying to cheat or anything, but I'm getting pulled on tracks with long starts. I have not done anything to my engine, completely stock. Parents tell me I have to do my catching up in the turns, but there are some jumps I can't clear right out of turns that the other kids can. I do well in all my races here in SoCal, top 5 in age group, intermediate and supermini. I just need that extra umph!! Help please, so I can relay the info to my parents.
 
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#5
fndaway66 said:
Thanks guys,

I'm not trying to cheat or anything, but I'm getting pulled on tracks with long starts. I have not done anything to my engine, completely stock. Parents tell me I have to do my catching up in the turns, but there are some jumps I can't clear right out of turns that the other kids can. I do well in all my races here in SoCal, top 5 in age group, intermediate and supermini. I just need that extra umph!! Help please, so I can relay the info to my parents.
What make/model 85 is it????
 

Jasle

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#7
do you race AMA??? Not much AMA in SoCal from what I remember. In our mod classes here in AZ .080 over is legal. You'll really need to check with your organization rules. I know AMA is big back east but the only AMA here is the Loretta qualifiers. Its really different out west. In our org the only thing you need to leave stock in the stock class is the displacment other than that anything goes. With that in mind you need to break out your rule book and see exactly what they allow. We have a joke out here. When someone asks if your motor is stock or mod you say its "califonia stock" which really means its .080 over.
 
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#8
You can still stroke the motor to max at 85cc, change ignitions, v-force or boyesen reed blocks, aftermarket pipe and cylinder work. Also, play with the gearing. Stock gearing for us was too low. Try going to a 15t countershaft sprocket. We were able to pull top five starts with a stock '03 RM85 w/ a 110 rider in supermini class running a 47t rear to 15t front.
 
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#9
Jasle,

Thanks for the info. I'm just worried about AMA because I want to try to qualify for LL this year. What exactly is .080 over and how or who can do this for me?

ktmdad,
Do you mean stroking the crank? I thought this would bring it up to 92cc? Illegal!! Correct me if I'm wrong.
 

Jasle

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#10
.080 over is an oversized piston. 2mm is roughly equivilant to .080" of an inch. so tht would be illegal if you were to go to the LL qualifiers. It used to be you could stroke or bore to get to 92cc's but aparently not this year.

If you do have it done just for home you can send your cylinder out to millenium or US chrome and steel for a bore and replate. They both do a good job. Buy your piston first and send it with the cylinder.
 
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#11
you can increase the stroke or the bore to get the maximum 85cc. Since there isn't a piston available for boring, your only left with changing the stroke.
 
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#12
And since your bike is already an 85...
your stroke increase would be zero. duh.
No overbores allowed in AMA for displacement classes
this year. period. LL or anything AMA.

Your options are porting the cylinder, cutting the
head(minimal improvement), a pipe/silencer(minimal)
and better gas.
I have NOT worked on the RM85
so I can offer no specifics to the bike.
 

oldguy

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#13
Watch any mods if you are thinking about trying to qualify for Lorettas in a stock class go here for the lorettas rules and info http://www.mxsports.com/frameset.htm

My son wants to try in the 125 stock schoolboy and from what we have found the only legal mods are bars (not levers/perches), jetting, and frame guards.
Holeshot devices are ok to be on the bike if they are disabled. No gripper seat covers or graphics.
Good luck if you try it
 
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#14
None of the 85's are exactly at 85cc. Stroking is an option, but the cost to gain an few 100th's of cc's is not worth it.