engine boggs down after letting off the throttle

[Guest]

I'm not sure what the problem may be but if I open the throttle up to 65 -75 mph and let off a little then give it more throttle it sounds like it bogging down. If I stay at a certain speed and or increase throttle it runs good no problems. What should I look at first? petcock, carbs, air cleaner. Thanks for any ideas.

[tom203]

It's probably just confused with "let off a little then give it more throttle " stuff! Does it idle nicely after a good run?

[scrapper]

not to bad I need to sync the carbs. It almost sounds like its sucks air when you hit the throttle again. It takes awhile for it to stop, 15 seconds sometimes a little more. It hasnt done it before. I was thinking maybe petcock was leaking or the rubber stoppers in the carbs fell off? I could try to set air fuel mix again maybe something vibrated loose. I am not sure what to check first. I dont want to pull the carbs off quite yet but will if I have to. I am sure a evil man had something to do with putting 4 carbs on these.

[tom203]

15 seconds is a long time "sucking air" sounds strange- any backfiring sounds? For starters, check that your air filter element is not torn. "Rubber stoppers"- you mean plugs over pilot jets? they are held in place by fuel bowl so they won't fall off.

[BassCliff]

Hi,

Does the air intake system have any leaks? Did you seal the air box? Have you replaced the intake boots and/or intake boot O-rings? Have you properly cleaned the carbs and replaced all the internal O-rings? Have you closely inspected the diaphragms on the slides? Have you first adjusted the valves and then sync'd the carbs? Did you use the "highest idle method" to adjust the idle mixture screws? Has the intake or exhaust been modified from stock?


Thank you for your indulgence,

BassCliff

[scrapper]

Carbs rebuilt new intake boots,o-ring kit,honda r/r, new plug wires. It does pop a bit and I started it and it backfired on the way home yesterday. Well it popped as soon as I hit the button on the starter. It wasnt real loud. I was just thinking it pops some when I am riding it, I'm thinking more so when I let off the throttle or give it throttle not at a constant speed, it runs good at a constant speed. I'm not sure about the airbox but will take apart and look.

[BassCliff]

Hi,

Good to see you've been busy with the maintenance.

It could be a little lean in the idle circuit. You could try turning out the idle mixture screws 1/4 turn to richen up the idle a bit. But, yes, go over the airbox and intake system to ensure there are no leaks.

Have a look here:

Idle Mixture Adjust Methods
(by Mr. koolaid_kid,Mr. tkent02, Mr. psyguy)

Thank you for your indulgence,

BassCliff

[scrapper]

I will check everything out tomorrow evening and saturday. Thanks for the help.

[tom203]

Check your petcock for correct operation;if it leaks fuel down vacuum line to #2 carb, it might cause some of your issues, yet seem (not as noticeable) to be fine at constant speed.

[scrapper]

Well I have been going slow but I did fix the reason it died on the way to work , loose wire. I cleaned the air filter and it was really dirty. That solved the problem except the popping is still there when I let off the throttle. I will check the petcock and the air fuel mixture and see what happens next.

[tom203]

If filter element is really old, consider getting new one (about $20 -for UNI-2440 ??); otherwise clean and lightly oil it. The popping does sound like a lean condition, so might be filter related.

[scrapper]

I probly set the air fuel wrong because of lack of experience. I may go ahead and get a new air filter but I will try to set the air fuel mixture first.
I have some green coils I can put on but need to find some plug wires. I am going to check ebay again. I will have to measure the lengths of the old ones first. Thanks for help so far.

[850 Combat]

Popping when you let off the throttle can be an exhaust leak.

[1_v8_merc]

I thought Generally the mixture screws only affect the bike at Idle-3,000rpms, otherwise you're running on Main jets. So if the problem is happening higher in the Rpm band, that should isolate it down to Electrical, Vacuum, or Fuel related?

[scrapper]

I noticed it does seem a bit louder also, so I will put inspection of exhaust on the list. How many miles before I check my valve clearance again? It only happens at higher speed around 55 to 70.