[ramprat06]

This certainly points to a carb set up in my opinion. A good cleaning is in order. Can you give us some more history on the bike? Mileage etc. It doesn't sound electrical to me from the description.



Thanks for filling out your profile information, that really makes things so much easier for us. You will get a lot of help here.

Welcome to the best CX/GL place on the planet.



Joel in the Couve

 

[ramprat06]

The best way to really clean everything out completely is by using an Ultrasonic cleaner with Simple Green. Harbor Freight has a good one many here have used, I think they are on sale now for $69 or so. You also need to get a very tiny drill bit for that low speed idle jet. That picture you posted is one from Larry ( LRCXed, our resident carb guru and moderator). He has written a book on this, but a lot of this information is posted in the Quick Reference section of the General Discussion topics.



It's hard to say why you are able to rev all the way in 4th yet not in 5th, but it may just be the carb has already bypassed the lower flows, and it struggles to get wide open in 5th. In any event, a more thorough cleaning ala Larry's way will surely afford you the peace of mind there, and then if the issue still persists, other avenues can be looked at.

 

[ramprat06]

This one?

Yep, that's the one.



And Nathan, a snippet from the post that is in the Quick Reference is worthy of copying here. Written by Larry......

As you know they can be a bit of a pain to get running right. The main issue they have is in the low to mid range RPMs. They have hesitations and flat spots as well as hard starting issues after years of neglect and sitting around with no use. What I have discovered is that the low jet that's pressed into the early style carbs, as well as the screw in style of the later model bikes, has been the culprit causing the issues we have been experiencing. The low jet has a very small hole in it (.018) and 8 holes for emulsifying the fuel. The .018 hole in the center of the jet has to be cleaned out manually with a drill bit to get it cleaned out properly after it is pulled out.



There is NO cleaner available including the Ultrasonic cleaner that will remove the deposits that build up in them. This alone makes a world of difference in how they run, but will not totally fix all the issues if the circuit chambers are not cleaned out as well. The book outlines a process to clean them manually, but strongly suggests using an Ultrasonic cleaner to do the job properly. Believe me when I tell you that these bikes can and will run like new when the carbs are cleaned and rebuilt properly. I have done a few hundred of them all with great success.

Let me add that I sent my carbs to him last spring for an overhaul and a week later they came back factory new looking and running, already balanced, and tested on the road. Well worth the $250 or so.