Engine bogs down

[mralex714]

I got my 86 back from the shop where they cleaned the carbs. The bike accelerates fine but once you get to a steady RPM the engine sounds like its not getting gas as if you let off the throttle. I swapped in a different TCI and fuel pump, same thing. I then changed the plugs with no improvement. I took it back to the shop and they are going to take the carbs back out. Any words of wisdom for them? Also the floats were changed.

[Venturous Randy]

Fuel filter?

RandyA

[SpencerPJ]

Possible gas line hose collapsing under vacuum? Some of those hoses are very thin walled

[Peder_y2k]

If the floats were changed, were they adjusted correctly for proper fluid level inside the carbs?

 

Also, the pilot screws may need adjustment to compensate for the age and wear of the engine (breaking-in). If they've never been adjusted, evidenced by the original anti-tamper plugs still in place, this could account for the bogging.

 

-Pete, in Tacoma WA USA

[mralex714]

If the floats were changed, were they adjusted correctly for proper fluid level inside the carbs?

 

Also, the pilot screws may need adjustment to compensate for the age and wear of the engine (breaking-in). If they've never been adjusted, evidenced by the original anti-tamper plugs still in place, this could account for the bogging.

 

-Pete, in Tacoma WA USA

 

He said the floats were adjusted properly. He used an EGA to adjust for the correct fuel ratio.

[Peder_y2k]

I had a professional 3 gas analog exhaust analyzer, but found the factory settings unworkable for my bikes, so I used old fashioned 'tuning by ear' to get the engines to run perfectly. Still thinking fuel mix is off, and likely the pilot circuit (pilot screw adjustment) is the culprit, presuming the carbs are well synched.

BTW, sold the EGA

Good luck........

-Pete, in Tacoma WA USA

[mralex714]

[quote name=

Also, the pilot screws may need adjustment to compensate for the age and wear of the engine (breaking-in). If they've never been adjusted, evidenced by the original anti-tamper plugs still in place, this could account for the bogging.

 

-Pete, in Tacoma WA USA

 

I tried adjusting the pilot screws and it made no difference.

[Huggy]

Carb sync?????

[mralex714]

Carb sync?????

 

Sync is good

[Peder_y2k]

I tried adjusting the pilot screws and it made no difference.

 

If adjusting the pilot screws had no effect, then there is definately something seriously wrong with carb function.

 

On my bikes, turning the pilot screws either in or out to extremes will cause the engine to quit frome either a lean mixture or a very rich mixture that will not combust.

 

Non reposnsive pilot screws is a real clue, that is to say that a radical mixture change is ineffective.

 

You sure that a pilot screw tip is not broken and stuck in the carb body?

 

-Pete, in Tacoma WA USA

Edited December 4, 2013 by Peder_y2k
spellcheck

[mralex714]

If adjusting the pilot screws had no effect, then there is definately something seriously wrong with carb function.

 

On my bikes, turning the pilot screws either in or out to extremes will cause the engine to quit frome either a lean mixture or a very rich mixture that will not combust.

 

Non reposnsive pilot screws is a real clue, that is to say that a radical mixture change is ineffective.

 

You sure that a pilot screw tip is not broken and stuck in the carb body?

 

-Pete, in Tacoma WA USA

 

I meant no change in my in problem

[mbrood]

You say it "sounds" like it's bogging down... with a steady throttle, does the rpm drop, does the speed drop?

[mralex714]

You say it "sounds" like it's bogging down... with a steady throttle, does the rpm drop, does the speed drop?

 

It has a moaning sound and the bike will slow down if you don't add more throttle. There is no acceleration you can only maintain speed and the tach does not drop. On take off from a stop the bike accelerates quickly, 6k is as far as I took it., with no problem.

[mralex714]

The bike is back at the shop that did the carbs, they are going to pull them again.

[mbrood]

Since you didn't mention a problem with idle... that leaves the idle jets and porting out.

Since you didn't mention a problem with acceleration... that leaves the main jets and porting out. It's when sustained fuel consumption is required. Did you try to slow and back off and immediately repeat the acceleration?

 

I would also question fuel pickup in the tank, fuel lines and possibly the pump.

 

I had a TR3 that would idle like a champ, accelerate like nobody's business and then bog... a fuel line was replaced and sliced open... it had internal deterioration and a small "flap" of line would lift to the higher fuel demand and contrict fuel flow until demand dropped and the flap "laid down". The outside of the hose looked older but no age cracks or kinks were seen. I always suspected fuel additives but what would I know.

[mralex714]

Since you didn't mention a problem with idle... that leaves the idle jets and porting out.

Since you didn't mention a problem with acceleration... that leaves the main jets and porting out. It's when sustained fuel consumption is required. Did you try to slow and back off and immediately repeat the acceleration?

 

I would also question fuel pickup in the tank, fuel lines and possibly the pump.

 

I had a TR3 that would idle like a champ, accelerate like nobody's business and then bog... a fuel line was replaced and sliced open... it had internal deterioration and a small "flap" of line would lift to the higher fuel demand and contrict fuel flow until demand dropped and the flap "laid down". The outside of the hose looked older but no age cracks or kinks were seen. I always suspected fuel additives but what would I know.

 

The guy that did the carbs replaced the fuel lines from the tank to the carbs, and I swapped a pump from another running bike.

[mbrood]

Then I would start getting more specific in the troubleshooting... is it better when you FIRST start out and gets worse as she warms up... is it gear independent... is it RPM dependent...?