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Stock Displacement XR70 Build

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Hey all,

i have a 2002 XR70R that I'm going to be freshening up. I want to keep the displacement stock, but add a little more grunt. It's pretty much bone stock at the moment, with the exception of a stunt50 exhaust tip. I also have a UNI pod and some jets to put on, but what else can add power for a stock cylinder and head? I know a full exhaust would be beneficial, as well as possibly a bigger carb. What carb? Cam? Valve springs? High compression piston? Thanks.

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A genuine Keihin or Mikuni 18mm carb with a pod filter really wakes the bike up. When I started out modifying my daughter's bike, the Keihin 18mm along with a FMF exhaust was a good combo. Another mod that makes a big difference in low end snap is to get a manual clutch kit. The auto clutch robs all the engine's snap.

If you're thinking of a high compression piston you would be further ahead buying a good quality 88cc big bore kit from TBolt USA. The stock 70 head flows better than the 50 head so modification isn't really mandatory. I also tried the TB Race Head and it wasn't much different. The V2 roller head is said to work but now it's starting to get expensive. At that point, a Piranha motor would be more economical and still more powerful.

Sent from my XT1650 using ThumperTalk mobile app

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1 hour ago, ohiodrz400sm said:

A genuine Keihin or Mikuni 18mm carb with a pod filter really wakes the bike up. When I started out modifying my daughter's bike, the Keihin 18mm along with a FMF exhaust was a good combo. Another mod that makes a big difference in low end snap is to get a manual clutch kit. The auto clutch robs all the engine's snap.

If you're thinking of a high compression piston you would be further ahead buying a good quality 88cc big bore kit from TBolt USA. The stock 70 head flows better than the 50 head so modification isn't really mandatory. I also tried the TB Race Head and it wasn't much different. The V2 roller head is said to work but now it's starting to get expensive. At that point, a Piranha motor would be more economical and still more powerful.

Sent from my XT1650 using ThumperTalk mobile app
 

I was looking and saw they didn't offer the 88cc kit without the race head. I have also always been thinking about the manual clutch kit, but it's the bike my friends ride when they come over, so that would make it a little harder for them to learn. The main reason I want to do stock displacement is I like being different. Everyone bolts on a bigger jug and calls it a day. I want a stock displacement bike that will keep up with 88cc builds. Also does anyone know about cams? Thanks. Also I found a 10.5-1 compression Weisco piston for cheap ish so I might check into that. 

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Screenshot_20170830-132027.png
The big bore kit is the Ist thing on the page.

The manual clutch is ridiculously easy to use on this bike. If they can't figure it out they aren't smart enough to figure out the brakes either.

Without carb, pipe and BB, I wouldn't worry about a cam. It's not going to do much.

Sent from my XT1650 using ThumperTalk mobile app

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To really be different, try going with a 48mm Wiseco domed piston (have the stock cylinder bored), the TrailBikes TBW0189 street cam, and the above mentioned 18mm Keihin or 19mm Mikuni-clone carb from Vince at T-Bolt. You'd be surprised at what the extra 5cc will do with the above parts used. And, down the road, if you toss in a TrailBikes 51mm stroker crank, you'll have 92cc of low-end torque to do 2nd gear holeshots all day long.

Edited by dirtbkr188
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That CHP coil is for a performance high-compression engine, it won't do anything for a stock 70cc engine

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16 hours ago, dirtbkr188 said:

That CHP coil is for a performance high-compression engine, it won't do anything for a stock 70cc engine

Sounds good! I just ordered a different one that's more cost effective, and I'm hoping it will solve my problem. I'm also grabbing some oil and a plug to freshen the thing up a little. Then the modding shall start.

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