Possible tuning issue...

[fzrbrandon]

Hope you all don't mind me putting this up here as well!

Hey guys,

So I've had this possible tuning issue for some time now. Basically, the symptoms are that at about 1/8 throttle (3k - 4k IIRC?), the bike sounds really boggy. You know that sound when the bike's starting to run out of gas (don't ask how I know)? That's kind of what I'm hearing. Once I'm past that throttle / rev range, she seems to be fine.

Here are my carb specs:

Main jets - 118 (DJ)
Needle clip - #5 (DJ)
Float height - 24mm
Pilot screws - 3.5 turns out (could maybe come out another 1/8 - 1/4 turn)

FWIW, the bike ran fine previously with these settings.

Here's what I have done:

Cleaned the tank
Replaced the fuel filter
Cleaned the carbs
*All jets soaked in carb cleaner, passageways sprayed and clear, etc.
Checked the air filter (K&N - clean)
Bench sync
Plug wires have been trimmed & caps re-seated
Caps are all within spec
Plugs are fine

Here's what I have yet to try:

Re-check float height
Double-check pilot circuit passages
Vacuum sync
Lastly - I'm fairly certain the valves need to be adjusted.

Regarding the valve adjustment, is it possible that the valves being too tight could cause this problem? Just today, I read a post from Reelrazor (Brutal Tooth's thread) that made me think that this might be a possibility.

Thanks fellas!
Brandon

[thatkid]

Brandon this is a tricky one.

*All jets soaked in carb cleaner, passageways sprayed and clear, etc.

How did you soak all 5 jets?

The Main Air Jets are none removable, without special tools.

Dare I ask, did you remove the Pilot Air Jets, & the mixture screws, including the spring, metal washer, and the o-ring?

Many think they have thoroughly cleaned their carbs/jets when they have not.

Keep us updated, & Good Luck.
Mal.

[fzrbrandon]

Brandon this is a tricky one.

*All jets soaked in carb cleaner, passageways sprayed and clear, etc.

How did you soak all 5 jets?

The Main Air Jets are none removable, without special tools.

Dare I ask, did you remove the Pilot Air Jets, & the mixture screws, including the spring, metal washer, and the o-ring?

Many think they have thoroughly cleaned their carbs/jets when they have not.

Keep us updated, & Good Luck.
Mal.

Okay, maybe not ALL of them - only the Main, Starter, and Pilot jets. I do, in fact, take out the Pilot screws as well and let them soak (for whatever that's worth). As for the Pilot Air jets, no, I don't take them out. But I do spray them pretty liberally with carb cleaner and blow compressed air through them afterwards. When I clean my carbs, I pretty much take them completely apart (without going as far as taking the bank apart - hard to get back together with only two hands!). I'm pretty thorough since I'm not too shy about doing it. Everything comes apart - slides / diaphragms, slide blocks, float assemblies, float needles, needle jets, needle springs, jet towers, all o-rings, the above-mentioned jets, pilot screws (and associated "let's see if we can roll under the table" bits)... whew! I'm definitely not one of those dudes that just pulls off the float bowl covers, sprays sprays some carb cleaner, and calls it good. So yeah, I'll probably pull them off again and give them another once-over but I'm fairly confident that they're clean.

[thatkid]

Brandon I thought you would do a thorough clean, That's why I pussy footed around, but next time you pull the carbs remove the "Pilot Air Jet" (NOT in the float bowl), and blast that passage way aswell

There are 5 Jets, 3 in the float bowl as you mentioned Main, Starter Pilot.

Then there's the Main Air Jet, and Pilot Air Jet, in the mouth of the carb. If those Jets are blocked your carbs aint clean. Many ignore those Jets.

Like I said yours sounds a tricky.

Mal.

EDIT:

http://www.cmsnl.com/yamaha-fzr600rd-19 ... /B-05.html

34: 8301423A77 JET.PILOT AIR

[fzrbrandon]

Brandon I thought you would do a thorough clean, That's why I pussy footed around, but next time you pull the carbs remove the "Pilot Air Jet" (NOT in the float bowl), and blast that passage way aswell

There are 5 Jets, 3 in the float bowl as you mentioned Main, Starter Pilot.

Then there's the Main Air Jet, and Pilot Air Jet, in the mouth of the carb. If those Jets are blocked your carbs aint clean. Many ignore those Jets.

Like I said yours sounds a tricky.

Mal.

EDIT:

http://www.cmsnl.com/yamaha-fzr600rd-19 ... /B-05.html

34: 8301423A77 JET.PILOT AIR

Sounds good Mal. I'll give it a go.

Just to add, this seems to make perfect sense since the issue is at such a low throttle position.

Thanks for your input as always!

[reelrazor]

Then there's the Main Air Jet, and Pilot Air Jet, in the mouth of the carb. If those Jets are blocked your carbs aint clean. Many ignore those Jets.

Amen!!

I have found that quite often this is ALL that is wrong and people go chasing their tails all over under the float bowls...The air passages are just as important as the fuel passages.

And, often a blocked passage will give 'opposite' symptoms..making a lean condition seem rich, and vice-versa