misfire

[jonyvtr]

hello ,

im from portugal ( a country where VTR1000 is a mirage), i bought a 1997 vtr firestorm 1000 with 27k km at a shop with waranty and everyting, good deal i tought, as it lasted only 150km in my hand, the front cct failed and i got stuck with a bag of nails, 1 month later they fixed it, it didn´t bent any valves because i was idling and it didn´t skiped any tooth. they changed the front cct and chain, bolted everything and started at first turn, idle is perfect in neutral it revs very nice too, the problem is under load. it misfires very badly and wont rev past 7000rpm, and makes a lumpy noise on low rpm under full load, under that it works fine and has the normal power, just cant get past the 7000rpm mark.
i let the bike there and they confirmed everyting again (so they said), cleaned the carbs as it could be a clogh... 2 months later i returned to get the bike, is was the same as before. now its my time to try to solve it.

can someone give any clue of what may be wrong?
it starts at firt turn even cold and without choke, idles perfect, has a lot of torque in low rpm like wen i bought it...

please.... help...

[MCN]

Easy stuff first.

Try to identify which cylinder is missing.

It can be simpler to set the idle RPM very low to where the engine almost cuts out.

Remove a plug lead. The engine note should change and the idle should get very unevn/lumpy/rough or the engine may cut-out.

That means that the ignition circuit and plug you disconnected is 'probably' good.

Do the test with ever cylinder.

If you remove a plug lead and you do not hear any change of engine note/idle then that circuit or plug is bad.

2) Remove the plug from the 'bad' cylinder and fit an new plug (or swap it with the plug from another cylinder.) Try to clean out the plug hole before removing the plug so that you don't drop any shit into the cylinder.
And don't bump the plugs, They are delicate/fragile.

Try the test again. If the problem is still on the 'bad' cylinder then it may be a coil unit.

3) Swap the 'bad' coil unit with another from the bike. It may be possible to simply swap the 'control' wires on the coils rather then having to remove and swap around. Wires can sometimes simply be moved instead.

Test again to confirm if coil is bad.

If the same cylinder is still bad then you may have a problem in the ECM or worse there could be a problem inside the engine. Broken valve, piston, piston rings. But check out the easy stuff first.

Since the fuel tank will be removed you may have to work out some system to fuel the engine with the tank off. It is risky to have petrol dripping everywhere so take the necessary precautions.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[jonyvtr]

the spark plugs have 50km, and it hard to identify what cilinder is misfiring becaus de engine hasno ability to rev past that rpm. even if you let it wide open throtle in any gear it wont rev to red line, the engine completly loses power, tomorow i will post a video of it starting and idling.
i read about an advanced thoot in any cam wold do something like this, is it true?
im a car mecanic so i dont have problems taking anything apart, i just dont undestand bike engine malfunctions other than the common crap that old bikes suffer from, like R/R, worn bearings and simple stuff.

tanks in advance

[Robby]

Take it back to the shop that changed the CCT and cam chain. It isn't working after they had it apart.

[andys675]

wrong plugs?

standard plugs are some expensive dpr9eix9 iridium

cam timing out?

take it back

and get manual tensioners, I had 2 go on the front cylinder, the third time it lunched the front head, including the cylinder
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Some people feel the rain, others just get wet.

[jonyvtr]

i solved the problem, it was the common 180 degrees off timming.