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550 running like "on choke" when hot.

Joined Feb 2012
20 Posts | 0+
Hi there!

My 550 has the following symptoms; runs very strong from closed throttle to WOT for +- the 1st 30min

Thereafter, on pilot jet, it literally runs as if the choke is out; sputters, won't idle etc. Once it manages to get on the main jet, it pulls like before again.

Other info:
-It has an aftermarket Leo Vince slip on.
-I increased the pilot jet from 38 to 42 IIRC.
-I also installed the Yamaha needle.
-Altitude = 4900 ft.

I reckon what happens is that the exhaust heats up the carb and this causes a lean condition?
Should I ceramic coat the exhaust inside and out in order to drop the temperature and increase the pilot to 48 perhaps?

Thanks
:)
 
sorry, it's 2006.

berger said:
Split carb intake boot?
Thanks,will have a look. Still strange that this only happens after riding for quite some time :cry:
 
berger said:
Split carb intake boot?
intake looks like new still.

The manifold between carb and motor looks to have a bit of a perishing going on but these are very fine little cracks and the manifold is thick rubber.

I will order a new unit and see if it helps.

Thanks for the help thus far.
 
ballbag said:
berger said:
Split carb intake boot?
intake looks like new still.

The manifold between carb and motor looks to have a bit of a perishing going on but these are very fine little cracks and the manifold is thick rubber.

I will order a new unit and see if it helps.

Thanks for the help thus far.
Yes, sorry if I was not clear. The boot from the carb to the cylinder head. They are known to split and crack. The vacuum leak will lead to idle and off idle problems. Not so much for mid range and above.
 
It seems that the O-ring on the intake funnel is not effective at sealing anymore.

It is very flat and appears to be bigger than the groove in which it needs to fit, causing the funnel to pinch it.
I will be changing the idle air jet from #100 to #75 as suggested by Taffi in another thread.

Part #87 on order:
 

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