Low speed miss

My 750 Maxim is driving me nuts! When starting out, giving it a small amount of throttle and slowly releasing the clutch, the bike starts missing badly, to the point it will barely accelerate. Once moving and giving the bike, say, 1/8 inch throttle, the bike takes off with good power and no missing. As long as you are giving the bike at least that much throttle, it goes like a scalded dog. It even idles great. I have cleaned the carbs twice even though I have not seen any sign of clogged jets or dirt. Valves have been carefully adjusted, have tried Sea Foam (did what I expected-nothing). Can not check float levels as the P.O. stripped the float bowl screws but levels have not been altered and the bike has always been a runner. Am I chasing my tail? Could a plug miss at low speed but run to near red line without a problem? Could I be missing some portion of the low speed circuit when cleaning the carbs? One thing I have not done is remove the mixture screws and blown cleaner thru there. Also, if I set the enrichment lever about half way on, the miss goes away but of course the idle speed is too high for safe riding. Could use some ideas. Thanks in advance.

 

You have problems with your pilot jets / passages. You can try to spray carb cleaner into the fuel tee and let the carbs sit for awhile. But ultimately the carbs will need to come off and get the "Old School Carb Cleaning Treatment" by Rick
As far as stripped screws and PO screwed over parts. Len @ xj4ever has everything you could need to replace.

MN

 

You skipped a step when cleaning the carbs, removing the mixture screws and jets.
Your problem is from the idle mixture on one or more of the carbs is not set correctly and or the carb sync is not set correct. Time to remove the carbs again to clen the idle circuits. while they are out try to remove the bowl drain screws so you can set the float levels. Float levels are also critical for proper carb operation.

 

Excuse my ignorance but are the mixture screws the ones I think they are - on top the carb, normally covered with plugs? If so, can I remove the gas tank, record the setting of the screws, remove them and spray carb cleaner thru there or blow out with compressed air? They were set with color tune plug and I have balanced them with four tube mercury balancer.

 

Mlew is correct I did forget to heve you remove the mixture screws. You can remove them and spray carb cleaner down there and that might help.

 

Thanks, will give it a try. Anything to avoid removing those carbs again. I don't mind the cleaning but the reinstall is a true tribulation! Also, if I run the carbs dry, would compressed air thru the mixture ports potentially damage anything?

 

Check for vacuum leak too

 

XJ wizard,
if I run the carbs dry, would compressed air thru the mixture ports potentially damage anything?

_________________
'82 XJ750 Maxim
'81 XJ750 Seca

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Porsche Boxster
81 Vespa P200
Columbia Moped
Peugeot Moped
Four Corvairs

 

No but you may want to open your bowl drain screws and put some hoses on and flush whatever may be in there out before you try to run the engine.

MN

 

And run some Stabil through the gas. It helps to free up sticky things in your carbs if you let your bike sit for any lenght of time.