yet another 1 cold pipe,2 hot 1 warm

[T-Dog]

I realize you more knowledgable folks have heard this a zillion times,I did search around and tried a few things,here's my little story...so I started up my 750T(1982 model),after adjusting the throttle cable,idle to 1k rpm,pipes 1 and 2 were really HOT(like right away),3 almost as hot,#4,could keep my bare fingers on,after letting the engine run for a few min's..There is spark to all cyl's,carbs have been cleaned new o-rings the whole bit,intake boots are fine no leaks and I added adhesive backed weather stripping to the airbox lid,to make sure it is well sealed.Airbox to carb connection is tight.I re-pulled the carbs to check the floats diaphrams, jets,no dice,bear in mind I'm no expert,but all looks okay..I did set the floats as described (and clarified by Basscliff).There is fuel in all bowls.My petcock appears to be working properly,flows on prime,not on on or res,doesn't leak.I tried putting a bit of oil in the #4 cyl plug hole,thought it would re-seal ring(found this idea while"searching" here )re-installed plug(all new plugs btw)got a puff of smoke on start-up(d-uh)pipe still cold.So I 'm stumped.Also,when I twist the throttle after letting the engine run for a bit,the it bogs a bit then"clears up "and roars at 5k rpm or so.Doesn't react immediately to throttle twistin" in other words,takes a second to react.I haven't adjusted or even checked intake/exh valves,I realize it should be done.Apart from that any ideas?I feel SOOOOO close to having a good running GS!!.... appreciate your input ,thanks all

[chuckycheese]

Valves

You should, by all means, check and adjust your valves....but I highly doubt that's the reason #4 isn't 'cooking'. As you know, a cold cylinder is really common here on the forum and, interestingly, it seems like it's almost always #4. I'll be curious to see what you find.

[almarconi]

When I have this problem it has been carb related. I would first check the wire and spark plug cap on that cylinder. All you need is a multimeter to check the resistance. A cap with open (infinite) resistance will not fire.

On the carb side double check that gas is getting into the bowl. When I rebuilt the carbs on my KZ I used a fuel valve (the little pointy thing in the carb)and valve seat from the rebuild kit. Turns out it was the wrong one and only a small amount of gas was actually getting into the carb, the bowl would fill but when you moved the float only a small amount of gas would come out.
Gas should pour out when you move the float. It is also possible that there is some crud inside the #4 carb. I am real leary about using the parts from the rebuild kits because althought the parts may look similar to the original(as in the case of that fuel valve) they may not work the same.

When you pull the plug on #4 is it when with fuel or is it dry?

I'd be willing to bet no gas is getting to that cylinder.

Keep us posted

[T-Dog]

almarconi,I visually checked the plugs for fire by grounding them to the head all had nice spark is that sufficient?fuel bowls fill,too,I loosened the drain plugwith a container to catch the fuel,plenty of that.Interesting point about rebuild kit parts,I used inlet valve seats and fuel valves from a rebuild kit,I kept the originals,I could clean and use them to take that out of the equation I guess.Maybe even re-dip carb body #4,I did dip all 4 of them,about 3 hours in carb cleaner,blew out passages with compressed air from a can,used a long fine wire aka "special tool"who knows stubborn guck in there,eh?Or new junk,I do have an inline fuel filter in place,though.Pulling off the carbs doesn't scare me anymore!I have a multimeter,I bought it just for this bike!where do I place the leads to check resistance(1 in plug cap obviously,right?) and what do I set m/meter to?my fuel air mixture screws are out 2 turns btw.finally first things first I'll fire it up and check/sniff the plug for gasoline and get back to you on that.Many thanks.

[greg78gs750]

uh, um, VALVE CLEARANCES!!!!!!!!!!! until you do this, all your hard carb work will be meaningless. really. i dipped my carbs twice, still had a cold #3, incidentally the VERY SAME cylinder that was still a little tight after a valve adjust because i didnt have the next size shim. so, i ordered it from z 1. installed it, checked all my clearances again, and, wallah, hot #3. it is easy, easier than stripping those carbs again.....

my 2 cents.

[chuckycheese]

Compression??

Once, again, I still seriously doubt that valve adjustment is causing your problem (I hope I'm wrong). But.......have you checked your compression on all 4 cylinders? I would be interested to know the numbers.

[rudy]

Leakdown tester will be a pretty handy tool as well (right up there with a shim changer and a bucket of shims). They can be had for $50 no fuss no muss, or built for cheaper by the thrifty handyman using parts available at a lot of tool stores. Tools are always a good investment. A compression test tells you that you have a problem with compression, a leakdown tester tells you what the problem is.

Personally, I have both, and use both just as often.


Edit: I see you're in Winnipeg. Find your closest Princess Auto. They regularly have the leakdown and compression testers on sale. VERY cost effective. I think the leakdown is actually on sale right now.

[T-Dog]

hi,been a while

valves are adjusted as per Mr. Basic's guide and Clymer manual.Same problem,cold #4 pipe&wants to die when I twist throttle....spark is good on all 4 cyl's so I suspect CARBS!My next bike will be FI!**.Any thoughts?Haven't checked compression yet.Also just noticed I'm gonna need a head gasket too,not valve cover, I re-used the old one just to slap it back together have new on hand now,but its looking ok.I might end up finding a storage space and working on it over the winter,with no garage its tough even in summer.The more I do it seems the more it needs!This doesn't discourage me,its an old bike and I love it anyway.Got a lot done this season,if anything next season I'll be riding it.Sorry long winded,thanks for your help,folks

[Baatfam]

I had the same problem with #1 after doing all you've done...cleaned carbs, new O-rings, adjust valves, check spark, everything...

I ended up just tearing down #1 carb again, back in the dip, redid the whole process and wham, bam, thank you maam....she was fixed...

I did all the carbs the same way....I guess there was just something stubborn in that carb...

Good Luck!

[T-Dog]

thanks Baatfam,my thoughts exactly,pull carbs one more time,re-dip,esp.#4.A mechanic friend suggested the same thing.I remain positive: I'm learning,and that 's good.

[chuckycheese]

Yeah, Dog............you're welcome.

[T-Dog]

Yeah, Dog............you're welcome.

I'll check compression too ,chuckycheese,as you suggested,and post #s,thanks for checking in

[chuckycheese]

Compression

Yeah, I'd be curious to see what your numbers are. I've got a tricky idea of something that might help but let's see what your numbers are first. There's really only a couple of things that could be causing your problem, at this point.