Carb issues...

Hi! so... my 1982 Maxim 750 is having some issues... i have gone through the carbs about 5 times now, im no expert, but i understand the principals behind their operation, when i first got the bike it did not even run, but now it kinda runs >.<

When i get it running (starts really well) i think its only running 100% on three of the four cylinders, and when i goose the throttle, it has really bad responce time, and it hangs up for a while at a higher RPM, it's lacking alot of power too... the carbs were FILTHY with solidified fuel.. but im pretty sure i have gotten it all out now.. but im at a loss of what to do now... any ideas?

Thanks, Largen.

 

Did you check valve clearance? Did you check compression? Did you swap out the plugs on the cylinder that is not fireing? Let us know.

MN

 

Checked Compresion, good on all four, just purchased all new plugs. and now it seems to be intermitant, seeing as the other three pipes get scorching ot, whereas the other one is only warm.... hmmm im so at a loss now XD

 

Sounds like that cylinder is not getting any fuel or not enough fuel at idle. Which cylinder is it? Maybe float level low on that one. Make sure you nhave spark on that one too.

MN

 

Sparks good, we found that its taking ALOT to fire it though.. i think it was up around 30k.... (we have some pretty handy tools) But its still a healthy spark... the float.. well i dont know how to properly set that, i just kinda eyeballed all four...

 

check the float levels on that cylinder, Since they have been gumed up you might have a stuck needle or something.

 

Well... i cleaned em really well.. everything seems to be moving well...

 

Is that plug wet or dry?

 

I have not checked... i should do that next time i start it i will take a look... i really should have looked the first time...

 

Doesn't matter, pull it and lets see if we can get you started in the right direction. Wet would be too high float level. dry could be low level and or plugged pilot circuit/ mixture screw .

MN

 

You really need to properly check and set the float levels. Eyeballing them will not be good enough.

Float Height
http://www.xjbikes.com/Forums/viewtopic ... t+dry.html

 

Get a Haynes manual and it'll show you how to properly do a float level. There's another technique done on the bench that I saw in Classic Motorcycle Mechanics Magazine.
You put the set of carbs in a vice, using a rag or foam not to scratch them. Use a level to make sure they're straight.
Drain all the float bowls.
Pour windshield washer fluid down the fuel hose until it backs up.
(You use ww fluid cuz its much less corrosive and dangerous than gas)
Zip tie the fuel hose to the carb rack so no fuel comes back out.
Now here's the trick part.
CAREFULLY remove float bowl #1 without spilling any of the ww fluid.
Using a vernier gauge, measure the height of the fluid in the bowl compare to the gasket face of the float bowl.
I think it should be 3 to 5mm.
If its not on spec, CAREFULLY bend the tiny metal tang where the float assembly pivots.
Put the float bowl back on the carb rack and refill with ww fluid again.
Repeat procedure until each float bowl measurement is dead on.

This method is a pain in the butt. However, according to Rod Gibson, the Master Mechanic/Editor of CMM Magazine, its the most accurate way of setting float bowl levels.
thx,
baz

 

Wow that sounds like a huge pain. A lot easier to use the tube method. But I can see how it would be accurate.

Interesting they suggest the washer fluid. We had a member have issues whit it not being the same when he used gas vs the fluid although I'm not really sure why it would matter.

 

Baz,

We tryed the window washer fluid trick and it did not work. The specific gravity is different than gas so the float levels were off. We nailed it useing regular gas. We also made the jig to hold that carbs out of wood. Its high enough to remove the float bowls and make adjustments and re-test.

MN

 

Sorry, i have been quite busy, but i actually just got myself a hynes manual, gotta love free downloads ha ha, and im going to have to try the method Baz666 said seeing as my drain scews are seized solid in there... and i dont have a hope in hell getting them out right now, they are striped like 150% so at a later date i might drill them out and Re-Tap them or something...

I will be un-able to work on it for another couple of days here... but this weekend (friday and saturday for me) i will have my paycheque and i plan on putting it strait to my bike, do you guys think its worth it to get some re-build kits for all four carbs? and anything else you guys may think would be wonderfull.
Thanks,
Largen.

 

I just had a revelation: if ou figure out the difference between ww fluid and gas, you can use t hat method and be right every time. Use ww fluid to get them all the same and multiply by the conversion rate to gas and you have the level they will be at with gas!!

 

That would be easy, have a float of some sort, see how far it sinks in gas, and how far it sinks in WW fluid, mark it out, and do a rough calculation, i myself think its just far to easy to just use gas, it does not bother me using something flamable, i have had my arms coverd in it before, no problem XD

 

Here are the results of Testing the two Fluids:

Start:
50 ml Washer Fluid
Insert Float (Top to Red XLarge Sharpie -- Pocket Clip removed)
5 ml Fluid displaced. Tip lowers to:
45 ml Mark
....................

Start:
50 ml Regular Gasoline
Insert Float (Same Float as above)
5.04 ml Fluid displaced. Tip lowers to:
44.5 ml Mark

45.00 - 44.50 = .05 ( +/- .01)

This is within .05 mm with Factory Specs being: ( +/- 1mm )

 

So there's not enough difference to even matter?