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problems with power xr600r help!!

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hi there, i got a xr600r 1998, i've done engine rebuild this winter and i have got problems with it's power. I've got new drilling new piston , new nearly everything that got somethin to do with power. Year before i had bigger compression coz piston was higier but it was in bad shape, now there is stock piston with 101mm bore. stock is 97 i think. Maybe power should be a litle bit lower coz of lower piston , but that much ? I cant even get bike to wheele on second gear with using clutch... Where can be problem ? I was riding friends TRX ( same motors, just 400) and it was riding like mad compare to my 600... Dont tell me that these bikes are that powerless ... Any ideas? how should i set up carburator ? Got everything stock there, jets, neddle everything.. Can it be by that ? Sorry for my english... im from god forsaken middle EU🤣👍 banna dance!

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I dont want to power it up by changing sprockets... i want to know if its something wrong with engine.. before engine rebuild with highier piston it was going fine with sprockets i use atm. I know that it was highier that means highier compresion, but it was badly damaged and now i got new one. i use atm 15 teeth front sprocket and 42 teeth rear.

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the nubers he quoted you are jet sizes for adjusting the fueling in your carb.

Does your bike start ok ? are your valves and timing right since the rebuild ?

Are your jets clear in your carb, if its a CV carb is the vacum diaphram sealed. if it leaks the slide wont open all the way on full throttle. run it with the filter off for a look.

Im no XR expert but most all singles are similar

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ye bike starts fine. Timing and valves are fine too, Seals in carb are fine too . I was wondering if problem cant be in jets? i got stock jet and bore is about 4mm bigger then stock from manufacture. Can it be ?

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Slight overbore shouldn't need a change in jetting. Lower compression is going to be noticeable, but the overbore should balance that mostly. You've got some other problem I think.

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right asuming our bore job was good and your rings are good, you will have good compression. asuming valve lash is set right.

HMMMMM???

Do you have stock intake and exhaust on the bike to go with standard jetting? A bit lean is usually fast until it blows up.

What happend to the first piston. Detination ?? you said it was badly damaged?

Asuming you have new fresh fuel in the carb . not old stuff thats been lying around. and you can see the main jet is clear when you rev it with the filter off. nice spray of fuel going into the intake. How about the spark. is it good and strong is the plug. good and the correct heat type etc .

Just more thoughts let us know

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Sounds like you have valves or rings that are leaking compression have you done a compression check?

Here's how to test them, you will need a compression gauge . First take a compression reading to see if it's on the low side"it probably is" and write it down for a reference, now put a few tablespoons of oil in the plug hole. If the reading goes up you have bad rings if it stays the same you have bad valves, that is if your compression reading is low.

The spec for your bike should be around 180 lbs of compression.

Also check to see if your exhaust valve is adjusted right and your exhaust valve decompressor is working properly and that your the cam timing is set right.

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damaged piston - rings were in bad shape so oil was eaten and one time i had no oil 👍 so imagine... i got stock exhaust , only muffler ( dont know if i used right word) is custom. I think that compression is OK , but ill check it . Decompressor is working fine. I think that sparks are fine. Maybe is how it should go... Maybe im not just used to it. I put yesterday 14 teeth front and 52 ( +/- few ) sprocket and it came a bit alive , wheeling a bit better🤣 but my max. speed is kinda low .. about 100-110 kmh donno how much miles is it. My opinion is : it can be a bad set up on carb or muffler. But i have no idea how technically can open muffler lower ur power , maybe u can tell me . I will be atleast smarter .) . I hope u understand me .. my english sux . 🙂

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First thing I would do is check compression, did you do a valve job on it when you rebuilt the topend?

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nope i didnt 👍 unfortunatly i was too lazy to check if they are good . ok ill try to check compression.

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Muffler isn't going to have anything to do with it unless it's plugged up or something. If it was fine before that's not the problem.

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