Tuning 32mm throttle body on my 899!

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Tuning 32mm throttle body on my 899!

well if you had 1000 miles no issues then i doubt its the tb that is the problem.. Although it might now be worth checking the condition of the plugs now you have done some miles.

Did this problem just start or has it got worse over time? Start by checking and double checking all the vac lines..
 
You have an air leak in the induction system. Basically there is more air getting in than the ECU thinks, the mixture starts going lean while on closed loop so the ECU chucks in more fuel, it balances out and starts to over-rev, goes too rich and then the revs drop as it starts to choke up. Then it starts to go lean again, eventually it all sort of balances up and the revs settle. Blipping the throttle and taking the ECU out of closed loop mode resets the whole process.

My son's Sei is doing the same but I'll be damned if I can find the blasted leak!

In reality it can only be one of a few places - the inlet manifold to head gasket, the manifold to throttle body gaskets (both of them) or the throttle body itself. On an 899 this is simplified a little but the fundamental problem remains. Check all of the joints that you have separated in the process of swapping the throttle body and spacer plates around.

Make sure the throttle isn't too tight as well, the engine tugs on it very slightly when it revs and it doesn't have a little slack it can go a bit mad.
 
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Thanks blu iv checked the plugs and they are perfect colour, the problem suddenly pccured after 20 miles of driving. Surely the top rubber peice wouldnt cause these problems though?

I now have taken the tb off, gasket seems fine and so do the rubber o-rings. However I noticed that the rocker cover gasket had oil all the way around it. I have a spare one lying about so I will replace that and all over gaskets.

Thanks for the help!
 
All fixed!
I noticed that there was a wierd sucking sound coming from the filter and decided it was the IAC.
Took it off and it seemed to be working correctly. However I found it wasnt able to move the whole way, thus getting stuck open.
Took the IAC off my old 30mm almost the same except the ends were different so I swapped them over.
That was it! A combination of bits and it runs perfect!

Now I can enjoy that extra power again ;)

Chris
 
Just an update to this thread :)

Everything has been running great so far with no problem (touch wood!)

However, i have noticed that when i start it up from stone cold, overnight or sitting more than 8 ish hours, it revs right up to 3000 rpm staying there for a second or 2 before settling down to the normal 1200 - 1500 rpm high idle.

Im a little worried as the high idles aren't good for the engine especially on 2C mornings.

I have reset the computer and there was no change, check coolant level and made sure it was bled properly. Not sure what else it could be :S

If the engine is at all warm it doesnt do this and just starts up normally.

Any help appreciated as always :)

Chris
 
My original tb never used to rev up so high however, I guess if everyone else does it then it's not a problem
 
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