Needle Circuit

[J_C]

ARRRGHHHH!!!

Test ride results: The problem still exists. However, I am now more sure that it is RPM related. Evidence to this fact:

Riding along in first gear with throttle cracked 1/4 or less. Smooth, no popping. At right around 4k rpm popping begins and remains up through 5 and into 6, where it disappears. I hover at 4.5k rpms and no clutch upshift, keeping the throttle in the same position. Rpms drop to 2 or so, popping disappears. As I slowly accelerate in second gear, problem happens again at the same point in the powerband. No clutch upshift w/ throttle in same position, rpms drop and problem goes away.

Curiously enough, while accelerating rapidly, as in 3/4 throttle or more, the problem either doesnt exist or exists for such a short time that I don't hear it.

Any thoughts?

[49er]

ARRRGHHHH!!!

Test ride results: The problem still exists. However, I am now more sure that it is RPM related. Evidence to this fact:

Riding along in first gear with throttle cracked 1/4 or less. Smooth, no popping. At right around 4k rpm popping begins and remains up through 5 and into 6, where it disappears. I hover at 4.5k rpms and no clutch upshift, keeping the throttle in the same position. Rpms drop to 2 or so, popping disappears. As I slowly accelerate in second gear, problem happens again at the same point in the powerband. No clutch upshift w/ throttle in same position, rpms drop and problem goes away.

Curiously enough, while accelerating rapidly, as in 3/4 throttle or more, the problem either doesnt exist or exists for such a short time that I don't hear it.

Any thoughts?

Sounds like you're definately lean on the needles. Lower the clips one position and try again. If we're right, it should then pull good right through the rev range.

[J_C]

Thanks 49er, I will. Though I'm still a bit perplexed. If it were the needles, then it should always exist on the circuit, not be a product of the RPM range. But I will adjust them. Nothing to lose but time.

[J_C]

OK folks, the needles have been adjusted. The clip is now on the highest setting it can be without adding washers to shim. This makes me a tad nervous. Especially considering that the problem still exists, although maybe in a slightly lesser form.

Observations from today's test ride:

1) Popping starts at 4k rpm. Stops around 5k-6k rpm
2) Popping does not exist on acceleration of 1/3 throttle or more
3) Popping only exists when maintaining throttle or slightly accelerating or decelerating (1/3 throttle or less)
4) While maintaining throttle position constant and rpm constant at 4-5krpm, if no clutch upshift popping stops until rpm range of 4-6rpm is reached.
5) Surginess seems much less than before raising the needles.
6) Much less popping on deceleration than before

[49er]

OK folks, the needles have been adjusted. The clip is now on the highest setting it can be without adding washers to shim. This makes me a tad nervous. Especially considering that the problem still exists, although maybe in a slightly lesser form.

Observations from today's test ride:

1) Popping starts at 4k rpm. Stops around 5k-6k rpm
2) Popping does not exist on acceleration of 1/3 throttle or more
3) Popping only exists when maintaining throttle or slightly accelerating or decelerating (1/3 throttle or less)
4) While maintaining throttle position constant and rpm constant at 4-5krpm, if no clutch upshift popping stops until rpm range of 4-6rpm is reached.
5) Surginess seems much less than before raising the needles.
6) Much less popping on deceleration than before

Have you checked the float levels are set at the correct height and the condition of your diaphragms?

Before pulling the carbs again, remove the pods and check that the rubber mountings aren't blocking any of the the vacuum ports. If this is happening, your diaphragms won't be operating correctly. While the pods are off and with the engine warm, try opening the throttle and watch for the slides to operate evenly. If one is sticking, it should be visible. Don't thrash the engine in this state, as it will run leaner with the pods off. You should be able to compare the slide movements at differing throttle openings without doing any damage. Just don't leave the bike running too long like that without using a fan.

[J_C]

The float levels were all checked when I cleaned the carbs (about 80 test miles ago) The diaphragms are all good. Only thing I noticed was that one had developed a very very small tear along the groove that sits between the carb body and the edge of the diaphragm cover.

Which vacuum ports are you referring to? I will definetely look to ensure nothing is being blocked.

Thanks for the tip on the filters. I'll take a look to ensure none of the slides are hanging up. I assume they should all rise in a relatively uniform manner?

[49er]

The float levels were all checked when I cleaned the carbs (about 80 test miles ago) The diaphragms are all good. Only thing I noticed was that one had developed a very very small tear along the groove that sits between the carb body and the edge of the diaphragm cover.

Which vacuum ports are you referring to? I will definetely look to ensure nothing is being blocked.

Thanks for the tip on the filters. I'll take a look to ensure none of the slides are hanging up. I assume they should all rise in a relatively uniform manner?

When you remove the filters, you should see an elongated port at 12 oclock. Sometimes the filters aren't the right size and when forced onto the carbs, part or all of the ports are blocked and don't allow the correct air flow to the diaphragm impeding the slide operation.

Check that torn diaphragm closely. I'm not sure where the tear is from your description!

[J_C]

I see what you're saying. I verified, at least as far as I could tell, there was no blockage ocurring with the intake port. I then warmed up the bike and removed the air filters. I reved the bike up to 6k or so, and I saw all the diaphragms get kind of bouncy, but they didn't lift up like I expected them to. I shut down the bike and used my finger to lift each one up and down to make sure they were sliding smoothly, which they were. As I lifted and dropped each one, I heard the puff of air from each diapragm. I'm not really sure where to go from here

For the diaphragm, the small tear is at the edge of the outer edge of the diaphram. I wouldn't think it's an issue because it appears that portion of the diaphragm is squished between the carb body and carb lid, creating a seal.

[Nessism]

Not sure it would matter but how is your carb sync and where are your pilot screws at? If you don't have a sync tool, I can help if you can drive the bike to Torrance.

[J_C]

Hey Nessism, thanks for your post! The carbs were synched using a digital synch gauge at KrisV's place. However, that was at 4000 feet, and back at sea level it ran very very lean. So I replaced the pilot air jets with a smaller size and went a few turns out with the fuel screws. I'm not sure of the exact numbers per carb, but I know that all four range between 3 and 4 turns out. If you think getting a look/listen would help I'd absolutely ride over to your place

[Nessism]

Hey JC,
I’m not a jetting expert by any stretch of the imagination but it sounds like you need to go richer on the pilot circuit. A quick and dirty test would be to take some duct tape and run a wrap around each pod to richen up the mixture. Might be interesting to see if this helps. Beyond getto tricks like this, I’m pretty much useless when it comes to jetting. I’d be more than happy to help it I can though.

[J_C]

That's not a bad idea, I can try that this weekend

I'm going to try to make it out to Chef's place, it's just so far away!

[J_C]

I was wrong, found an email to chef a few weeks back:

1 - 4.5 turns out
2 - 4.5
3 - 4
4 - 3.5