build sugesstions

H

hansshanks

New Member
Jul 8, 2010
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ok fellas. i am ready to spend some coin on my sons blaster. he is 12 and moved up from mini quads this spring. he rides and jumps the piss out of this thing. he needs more power. he short shifts alot so i think a bottom to mid power range would suit his style best. he came off pitbike engine powered mini quads. right i am thinking vitos ported piston, vitos hicomp head gasket, oil block off and fmf pipe for motor. that the combo some of the local guys runs seems ok. we race flat track, tt, sometimes motocross, and a bunch of sand.

suggestions welcome as well as any used parts to save a buck. i have till nov 19 to have this thing ready to race.

thankd for your time

hans
 
do this instead.
port the jug
have the head cut/redesigned
FMF pipe will be ok
since he likes to jump, if you have money get some elkas or works shocks, if you dont want to spend that coin, get some banshee front shocks and a 400ex rear shock.
 
Search ebay and craigslist for used parts. Don't forget tires. The head gasket won't do anything for performance, unless it is super thin. Try to teach your son not to short shift too. Reeds will help out with power and air cheap.
 
eeeeeeewwwwwwwww vitos piston, or basically anything, ask free what he feels about them, and always stick with oem gaskets, ask Oconner racing or awk about them.

I say get a trail port job and redesigned head from ken, and a wiseco piston, and i nice exhaust, f7 is good, fmf gives good low end supposedly though
 
well if your on a deadline of 19th your not going to have time to get the topend ported by a pro but if you have a dremel you could watch ken's diy on it but i wouldnt worry about raising the exhaust port because the vitos piston has a dish cut on the exhaust side to simulate the raised exhaust port by lowering that side of the piston. i dont know if its a high comp headgasket but a basegasket. i would stick with an oem basegasket. i have been running my fmf and its a great low mid pipe. you can do a timming advance yourself without buying anything there is a diy on that too and should also help with the bottom end. if your rebuilding the topend you could also get the head redesigned and milled. a set of boysen replacement reeds are inexpensive and will help the bottom end too and if you wanna go top of the line ther is the vf3 reeds. If he is jumping i would recomend at least the 400 rear and banshee fronts, it really helped me from bottoming out of course im a little heavier that him i think.... ken has a bushing kit to basically bolt up the 400 rear shock. have you flipped the front tires? this will make it a little wider up front and its free. he will also benefit from some aftermarket rear tires if you havent got some already. good luck!
 
i have already put my yfz hubs on the rear as well as my set of baja t9 fronts and hiper rears plus full set of holeshot sx mx tires it. prob now is gearing is way to short which i think is agrivating the short shift problem till he gets to third hear. and it finally gets traction. he hasnt mastered the feathering of the clutch. ridden forgiving fourstrokes for to long. will the mods recomeneee keep up with midly moded raptor250
 
hansshanks said:
i have already put my yfz hubs on the rear as well as my set of baja t9 fronts and hiper rears plus full set of holeshot sx mx tires it. prob now is gearing is way to short which i think is agrivating the short shift problem till he gets to third hear. and it finally gets traction. he hasnt mastered the feathering of the clutch. ridden forgiving fourstrokes for to long. will the mods recomeneee keep up with midly moded raptor250
Click to expand...

with what is suggested u will embarrass a rappy 250
 
ok i got er opened up and have a 65mm piston and a .8mm thick head gasket... whare stock specs. wanna make sure this is original
 
Hans check out my sig and avatar pic. This 04 is raced by my son in MX (OR state champion 2 years). He kicks ass on everyone but a couple heavily modded rap250s ($15K+ bikes). Engine work is great but WIDTH (A-arms) and SHOCKS make the most difference, taking corners and jumps fast . The more stable it is and better it rides the faster he will be able to ride it.

YFZ shocks on long travel a-arms is a semi-budget way to go. Rear spacers (solid-block-type) if you can't afford an axle. Never used the 400ex shock but people say good things, the 250R shock is only slightly better than stock. Works or equivalent is the way to go.

You've got to teach him to wind it out a bit, by short shifting he is cheating himself.

And yeah, gearing is an issue. You want to pick up a 14-tooth front sprocket, at least, for 14/40 gearing. 14/38 might be even better, haven't tried it yet tho. Lately he's been practicing a 2nd gear start, 1st just spins the tires.

Search ebay for kx85 or yz85 carbs, etc. If the pic shows a carb with a slide cover that is held on by two screws instead of a screw on cap, then it is a KEIHIN PWK28. This carb (properly jetted) and an open airbox with a UNI filter made a respectable increase in power over the stock carb. You can pick them up used this way for about $50. It is the combo that is now on my 94, I moved up to a ported jug and bigger carb this year on the racebike.
 
Last edited:
his is getting better at the shifting. i have already put my full set of hiper bead lock wheels and holeshot sx tires on it with my yfz hubs on the rear. i am trying to get him redy for flat track. i think i am going ot go with a vitos ported piston, hi comp head gasket and a fmf pipe. and then spend the rest of th emoney on suspension, sway bar and flat track tires. then get the shocks valved for jumping in the spring. this the motor set up that a couple guys here local are running with good luck. and hopefully i can get the head and cylinder sent off for some porting over the christmas break.... oh and i put the 14 tooth on it and he has been doing second gear starts since right after we got it. because first goes no where.
 
his is getting better at the shifting. i have already put my full set of hiper bead lock wheels and holeshot sx tires on it with my yfz hubs on the rear. i am trying to get him redy for flat track. i think i am going ot go with a vitos ported piston, hi comp head gasket and a fmf pipe. and then spend the rest of th emoney on suspension, sway bar and flat track tires. then get the shocks valved for jumping in the spring. this the motor set up that a couple guys here local are running with good luck. and hopefully i can get the head and cylinder sent off for some porting over the christmas break.... oh and i put the 14 tooth on it and he has been doing second gear starts since right after we got it. because first goes no where. and i ordered the his short turn vortex twist throttle kit today. the turbo ones arrived but they are regular cr style full turn. so sending the turbo ones back
 
ya pretty big differences. i mostly just put swaybars and owering kits on and off. run mx set up other wise. i narrrow the rear of mine. but not on my sons since he has less powere and needs the width to get it to side
 
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