R1 4xv wont rev

[metro1]

Hi im having trouble with my yammaha r1 engine.I blew the last one up.I sourced a new one with uprated carbs and an uprated clutch.It took a while but i eventually got it in and more or less set up how it should be.I just had a couple of small bits to do.so we decided to start it up and see how it run before sliding the engine back.New oil filter and coolant went in.After a couple of attempts we got it started.It ideld fine so we rolled it out of the garage let it warm up and give it a few beans.But it wouldn't rev over 6k so we presumed there was a problem with the carbs so we took the new carbs of and refited the carbs from my old engine and had the same problem. Any ideas.

[Turn7]

I would assume the original carbs were dynojetted or similar and as such the OE carbs wouldnt work.

If thats the case, ahve you checked all the fuel lines to make sure none have been kinked or pinched on the new install ?

[metro1]

the original carbs were the standard bike carbs with a k+n filter in the airbox.Im unsure what jets they have in them as i have never looked.The new carbs have an ivans jet kit already fitted when i got them along with a set of trumpets and a pipercoss filter that goes over the top doing away with the filter.I have tried both sets on the engine and get the same problem the fuel line is routed in exactly the same way as it was on the old engine.There are no visible kinks or pinched points.I am beginig to wonder if ever the main jet is wrong,theres a problem with the fuel pump or the timings out.

[Turn7]

Your first set up - you say it ran the airbox ? If so, when you swapped the carbs over, did you refit the airbox assembly ?

[metro1]

no the new ones used a difffrent setup, i put the old ones back on minus the airbox and had the same problem i can try refiting the airbox on the old onrs to see if it makes a difference

[Turn7]

I would definitely put the airbox back on with the carbs from the original setting.

You know that set up worked,so if the problem remains, you should be able to discount carb set up.

If you get my drift....

[TallPaul]

I know its a different engine, but my old Yamaha FZR1000 EXUP (the bike before the R1) had a similar problem in that it wouldn't run past a certain revs, it turned out to be the CDI box. Might be another thing to check.
If you're running with the EXUP valve, check its opening and closing, snapped cables or a seized valve can give problems too.

[metro1]

i will try adding the airbox and see what happens, as for the cdi box for some reason its running a more modern one i think as it doesnt match the spare one i got with the new engine but if the old one ran on it and there the same that shouldn't be a problem.i will see if i can find another one and try that.I am not using an exup valve in the exhaust system.I am begining to think its a timing isue

[metro1]

got it running right today and managed to fit the new carbs.The throttle sounds a lot more agressive i think im in love

[Turn7]

what did you do ?