need carb help

Hi Folks,

I have an '82 XJ750R Maxim. Have rebuilt carbs many times. Gas overflowing out the intake, so i rebuilt this spring...and still overflowing. Everything replaced BUT the floats as i cannot find any new ones i trust to be "new". Is there something i can coat the old ones with (knowing that the friggin' alcohol reeks havoc on most everything) or am i stuck with finding replacements? And if so, can someone point to a source?

Many Thanks in advance.

Cheers--CB

 

Hi CB . Sorry to hear you are having problems after replacing so many parts of the carbs. My experience tells me that it is very unlikely to be a problem with the floats themselves. It is much more likely to be caused by incorrectly set float heights. You didn't say whether you wet-set the floats heights with the carbs off the bike and positioned level. It's a painstaking task but absolutely essential for correct operation. RickComatic posted a very helpful guide some time ago. Try searching "Church of Clean". Hope this helps and good luck.

 

agreed, the float needles and seats in some kits are known to cause problems. click the xj4ever banner on top right, start a conversation with "chacal" he can fix ya up.

 

Thanks. I have not wet set them as yet and my experience is much the same. I was going to check that next before ultimately deciding that it was indeed the floats. However, i have done this many times and never had this issue...so something new is going on...thus my conclusion that it's the floats (i also noticed in at least one float had a mark that is likely a hairline crack). It was running fine last fall and a few times this winter when starting, but it began dumping gas at one point (first time ever for that). The shop may have done that many moons ago for me when they were last balanced...but i am making a wild guess that the floats are original. I've had good success in the past when simply removing everything and very carefully reassembling being extra careful not to tweak the floats...then run it into the shop every few years and have them balance as i am not set up to do that. In any case, that's what i know just at the moment. Next time i am able to get it apart, i will put it on the bench and see what gives. I'll dig into the Church of Clean as you suggest...I can assure you, "clean" is not part of the issue...very tuned in to that aspect! Cheers.

 

thanks i'll give that a go. Cheers.

 

The Hitachi floats rarely fail, they're solid (unlike Mikuni floats, most of which are hollow). You can try "floating" the floats in a bowl of any liquid to see if they do float, and even hold them submerged for a hour or so (see if any air bubbles rise from them) to see if they take on water (or weight more after submersion).

Most likely, it is either a fuel level issue or the float valve needle/seat/gasket are bad, hung up, etc.

 

I definitely had issues with sub par float needle assemblies, particularly if they were longer than the originals changing the geometry on the float tang to float valve. Finally got a good set from Chacal at XJ4ever that matched the originals very closely.

Here are a couple of links to help out:

http://www.xj4ever.com/setting%20fuel%20levels.pdf

http://www.xjbikes.com/forums/index.php?threads/in-the-church-of-clean.14692/

 

Are your needle valve assemblies matched sets, or did you get the valve bodies one time, and the needles another time or place?

 

They came as a complete kit. I've bought the same ones from the Yamaha shop here in the past. Guess they could be different. I'll check a little closer. Major point is though that the leak started before the rebuild, and is unresolved with the new kit...so a little confusing.

I'll check the float levels first chance i get. Thanks all.

 

Are you running a fuel filter or at least know that your petcock filter is good? I had some crap in my Kaw tank get into the carb and jam the needle, caused it to leak severely at work one day. Cleaned out and added a filter, never happened again.

 

petcock is all clean and looks good...vacuum type and checked for open/close. No additional filter. Tank is very clean as are carbs...I've never had any crud in the system. Any debris has always been from the jello out of the gas if I forget the stabil during the winter.

 

Good deal. You must have something going on with the needle and seat then. That's really the only thing that would make it fill up to the point of overflowing out the intake unless your fuel line is hooked up to a vac/vent port or there is something seriously wrong with the carb body itself.

 

If you wet set them then you should easily see the carb(s) that is (are) leaking. Once you get them set and the leaking stopped, empty the bowls and let them refill a couple of times just to make sure you don't have a sticking float or needle. By the way, I got the solid brass needles and seats from Chacal and have had zero problems since then.