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88 kit installed. WHERE'S THE TOP END?

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Just installed my tb88 kit on my xr70. I really didn't notice much in the way of more power.

The kit was used but in good shape. Old tb racehead and 20mm carb.

In first off the line it feels stronger but on the top end not so much.

I'm running the stock pipe w/ the spark arrestor removed.

Could this pipe be killing my top end power?

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for power you need some kind of back pressure and with you spark arrestor out you dont have any! an aftermarket pipe will be better, thats why they cost some good money. i dnt know but i heard you might have rejet? maybe someone else can answer that?

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If people are removing the spark arrestor for gains on there stock engines than I don't think it's going to hurt a bigger than stock motor.

The pipe probably can't flow enough air even w/ the spark arrestor removed.

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If people are removing the spark arrestor for gains on there stock engines than I don't think it's going to hurt a bigger than stock motor.

The pipe probably can't flow enough air even w/ the spark arrestor removed.

True true true that crappy stock pipe gotta go. I don't understand why you don't have good response on your 88 kit. Maybe you should reinspect the used set up. Check out the valves,springs and tapet spacing. Did you overhaul the cylinder? I would have I mean it's used and it was off at the time. Rehone the cylinder get new piston and rings. No rejetting needed ,but definately get a aftermarket pipe. Don't cut corners with a good pipe either. Spend the top dollars and get top results. Everybody has there opinion on which muffler is the best but its only like probaly 5.Now which 5 do a poll and everyone will tell you.

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You could be running rich b/c of that very restrictive exhaust. Get a different pipe and adjust your jetting to match.

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If people are removing the spark arrestor for gains on there stock engines than I don't think it's going to hurt a bigger than stock motor.

The pipe probably can't flow enough air even w/ the spark arrestor removed.

it hurts performance more the smaller the motor, people who do it are clueless and think more sound is more power. the stock pipe is not your problem.

do the ports on the intake match the head?

you definetly need to rejet the carb.

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it hurts performance more the smaller the motor, people who do it are clueless and think more sound is more power. the stock pipe is not your problem.

do the ports on the intake match the head?

you definetly need to rejet the carb.

A larger exhaust will give you more gases flowing out which will allow you to flow more in when you bore the motor and add a bigger carb(which is what he has). One thing a better flowing exhaust will hurt though is throttle response if you don't have it tuned correctly.

You are right about a stock motor. Taking out the arrestor kills throttle response b/c there is almost no back pressure. And it doesn't even sound good. I don't know why people do it and say it's better.

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the header matched the head, its not gonna be a problem.

aftermarket exaust will make it run leaner and probly push his jetting closer to what it should be, in that somewhat expensive way, fix the jetting in the carb.

just like you said the higher the velocity the better, you wont get "more" exaust escaping until you get into the high rpms. does not sound like a problem.

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Thanks for the replies guys,

I did inspect the parts and they looked good enough to put together.

The guy sent the spark plug he was using so I could see how it was running on his bike.

I ran it a little tonite and the plug which was close to perfect before I ran it, actually looked a little lighter on one side of the electrode than the other.

I would think that it's running lean. With my stock pipe vs. his old hi-dollar pipe I find this hard to believe.

I am going to get a new plug tomorrow and see what it looks like after running it.

I still have the 13t front sprocket on it and might go back to the 15t.

In 1st, I noticed a difference in the amount of effort it took to wheelie, a lot less throttle and jerk to bring it up.

So it's working good down low, I think it may be lean on top, from the plug reading and not much power.

The head and intake ports looked matched, didn't see any reason to mess w/ that.

The intake had been modded to work on a 50 w/ a perimeter frame. The intake had been cut and rotated to clear the frame. The work looks good though and fit my bike fine.

Someone said something about a washer under the needle.

I thought they did this because the needle wasn't adjustable, but mine is and it's all the way on the bottom clip position.

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On the TB 20mm carb it is a mixture screw. As a general rule if the adjuster is on the air cleaner side of the carb it's an air screw, meaning the more it's turned in the less air flows=richer. If the adjuster is on the engine side of the carb it's a mixture screw and the more you turn it out=richer.

Regarding your top-endless motor:

1) Double check that you have the cam in time properly.

2) Do a leakdown on the motor to see if the valves and piston rings are sealing properly. If you don't have a leakdown tester take it to a reputable mechanic and let him check it out.

3) My TB 88 is set up with a stock pipe and runs just fine--I've actually beaten 125 Pitster Pros to the first corner (and no, I'm not a superior rider, just an old fart). A loud pipe might help the way it runs on top but not that much.

I suspect that you have a problem with the condition of the top end of your new motor, probably needing a valve job or corrective action in the piston/ring area.

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Well, rode a little and checked the plug,. Plug was tan but lighter than it was originally.

Checked my valves and they were a little loose of.003, so redid those.

Carb had a 85 main jet w/ the needle all the way up.

Changed to a 87 w/ same needle position. Waiting to check the plug.

Probably going to move the needle back down some,. but will have to wait and check the plug.

Felt better on top w/ no poping on decel. Mid range felt a little slower. Felt like a bump in the power band in the middle.

I also took off the 13t and put the 15 back on.

We will see.

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Well rode quite a bit yesterday, in the 95' heat. After changing to the 87 the plug darkened up. One side was black and other was closer to tan. Haven't messed w/ the needle.

I did get a cheapo rear shock for the bike, put it on. It is way better than my stocker w/ my 2in spacer I made. The shock has a tire valve on it. I pressed the stem and an oily substance under pressure came out. What is that valve for?

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hahaha! you just ****ed up your new shock.

that shrader(sp?) valve is were they put in the compressed nitrogen. now that shock needs to be rebuilt and recharged.

are yo doing proper plug chops or just looking at the plug?

hold the rpms at a constant rpm for no less than 20 seconds.

hit the kill switch and shut the throttle at the same time.

pull the plug ASAP.

then check how it looks.

your looking at just the insulator(white part around the electrode) not any of the metal.

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I don't think you screwed up your shock. I think it was already screwed up. Oil is not supposed to come out of that valve, just nitrogen. Did you buy it used? If so, I would ask for my money back. And if it is new I would get my money back and tell everyone the name brand.

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leaner when turned out on the air screw... as for the power lacking... double check the cam timing... with the "T" mark lined up most of the time the "O" on the cam will be just a hair above the mark on the head.

most of the time the cam timing is off when you get the symptoms you described... the stock pipe shouldn't be hurting you that much.. i still run a stock 50 pipe on my 88 race head adn it's got a ton of top end.

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hahaha! you just ****ed up your new shock.

that shrader(sp?) valve is were they put in the compressed nitrogen. now that shock needs to be rebuilt and recharged.

i don't know why you find it funny that some one made a mistake.. i'm sure there was a point you didn't know what you were doing and probably screwed something up too... did you like when people laughed at you?

anyway.. that valve IS for nitrogen and oil shouldn't come out of it. you can have the nitrogen recharged at most larger bike dealerships for around 15 bucks

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Thanks everyone for there replies. I'll check the cam timing again and see what it looks like.

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TurboGlenn, Thanks for trying to check the &%$#@! (50addictedtosuckingcock)for me.

That dude is always being an ******* to someone.

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