Bowl levels are the same, sooooo.....

[Hoomgar]

No one touched on the holes in his exhaust? Scud, you mentioned rotted exhaust pipes. Was it the pipe in question that has the holes? Exhaust leaks can also have an affect on combustion. You could be having a combination problem. Please give more details on the condition of your exhaust buddy.

 

[Scud]

Sorry for the long delay....I am in Montana and away from internet for the most part until this Wednesday.

Holes in the exhaust....well, both sides have holes (1/8 inch) and gashes up to one inch in length by 1/8 inch along the bottom side of both pipes. In fact, last week I had a short of some sort that made the engine stop for a second or two and then start, this led to a backfire that blew a one inch by two inch piece (torn on three sides and hanging from the attached piece) on the number three and four cylinder side (right), I was able to fold it back into place without it breaking off.

I checked my harness and found a suspect wire that I fixed and the problem went away.

Question, do you think this has something to do with my problem even though it is on the right side exhaust pipe??

Which leads me to another question....anyone have stock exhaust pipes for sale that will fit my 1980 GS 750E...I am in the market now. :?

Thanks,

Scud

 

[Hoomgar]

I am not the expert but I know enough to know that major exhaust leaks like your describing can have a serious impact on how the bike runs. I am surprised that none of the guru's picked up on that when you posted it last month.

What affects exactly it would have is what I don't know but I am guessing that yes it could be related to your problem or at a minimum could be compounding it.

 

[Scud]

Thanks Hoomgar, I thought that a while back but since I had not heard back I figured that it may be alright to leave it as such since it was on the bottom and not cosmetically visible unless you looked underneath the pipes.

I guess it is time to look for a set of pipes. I really like the stock set even though they are hard to find.

Scud

 

[gsBert]

well, seems like the new plus picture is indeed leaner than you'd want it.
i don't think it's too dangerous but it might just be because i haven't holed a piston yet.

so the concensus seems to be: fix it.

i feel like a noob for not picking up on the exhaust bit, that could indeed be it (me being a noob, and your lean being exhaust)

1100 pipes should fit your 750, that's what i have on mine.

i find it better to put a 4:1 system on there it's lighter and won't leak as easily. you might want to look into that. shouldnt require rejetting if you're still using a stock airbox if you buy a street legal 4:1...

 

[Scud]

I have saddle bags (actually suitcases) that ride near the OEM exhaust. Aftermarket pipes have a tendency to ride higher and I think would interfere with my suitcases (samsonites!).

I have not ridden her since the last few posts and will more then likely not until I pull the carbs....good incentive....

Scud

 

[Scud]

I'm back.. GSBert, Hoomgar, Keith and all, I took the carbs off last night..do not know what got into me..maybe it was all the rain outside ...anyway here are the specs on the jets in my carbs, all have the same jets installed.

Mains 112.5
Air 170
Pilot 42.5

I live at 6,200' and have all the floats set at 22.4 mm.

I looked at the carb in question (#1) and it looks fine...hmmmm... I cleaned all jets and re-installed.

Also, I ordered a Vance and Hines 4 into 1 so I will pull the pipes off today and get ready to install those as well, should be here next week.

Anymore thoughts or ideas?

Scud

 

[KEITH KRAUSE]

Well at least you know the jets are the same, at least the ones you looked at. I suppose #1 could have a leaner needle jet or something else going on. Who knows the carbs history? I'm not reading back to see what's been done but I know we've tried to cover everything.
The pipe will require some re-jetting anyway, at least the main jet. And now you won't have any negative effects from the bad exhaust. I do suggest new exhaust gaskets though.
Obviously, somethings causing that cylinder to run leaner than the others, but who knows what?
After you get the pipe on, I would double check the vacuum synch. At least hook up the tool and read the levels to see if they're still as you set them. I suggest this because many times the synch "changes". Most of us have set a level, tightened the adjuster screw, but lo and behold after exercising the throttle a few times to verify, the level changes a bit. Maybe you'll find the level off a bit (lower) if you re-check?
If it still runs leaner than the others, maybe we can all get together and make a check-list of every possible lean condition, regardless of how remote the chances.
By the way, taking plug reads at different throttle positions can possibly narrow the cause down too. You may find the plug starts burning more similar to the others at a certain throttle position. For example, it may burn similar to the others a full throttle, but quickly lean out at 1/3 throttle or vice-versa. It may be lean at minimum throttle, etc. Marking the throttle and taking various reads has always been a good way to trouble shoot. If I remember, you haven't tested in this way. And I mean at a solid 1/3 throttle, chop off and read, then full throttle for the main, then mimimum throttle for the pilot circuit. Might tell you something.
But I'd first triple check the vacuum synch.

 

[gsBert]

congrats on the carb teardown scud.

as keith mentioned: did you look at your needle jets (the tube the needle under the diaphragm slides in and out of)?

the different throttle opening plug chop will indeed narrow the lean condition down to the range. if it's all across, blame vacuum leaks or compression, else you got one weird jet or somethign else wrong (hope its not something else cuz its gonna be a female dog to track down)

you kow how to do the plug chop right?

this sounds dumb, but you did make sure none of your diaphragms had holes in them right? (it's too obvious, i'm sure you checked)
my carbs also have vacuum nipples on the diaphragm cover. they should all be plugged except for the one going to the petcock. tripple check that too.
let us know. good to see this thread progress.

 

[Scud]

Keith - I will take out the needle and remove the jet that has all the holes in it that the main jet threads into and the needle slides in and out of...what is that called anyway (thanks gsBert)??...and make sure that all holes are clear. Also, Keith you mention exhaust gaskets, the originals consisted of two half moons only on cylinder exhasut ports one and four...does this sound right?? The fellow I purchased the bike from was the original owner and very detail oriented, I knew him personally before he shed the wing of his Maule aircraft at 100 feet AGL and he died as the result.

Hmmmm...diaphragms...I looked closely at all and did not see any tears...those things freak me out...they seem thin to begin with and I do not want to F#$K them up if possible.....so I have been REAL gentle with them. gsBert, my carbs do not have anything on the diaphragm cover, just a solid aluminum cap.

I will also do a plug chop and kill the engine at high, medium and low rpm's ( I have the perfect, untravelled road for that test) and let you know what I find wtih regards to plug color.

As mentioned, my new pipes and larger main jets arrive next week...then the fun begins again. I have performed a few synch's and own a Morgan carbtune..love that thing..

I also am waitning for a new valve cover and breather gasket alon with the end plugs.

I am off on a business trip tomorrow and will return on Sunday night to check this post.

As usual, thanks for all the information and ideas, we will figure this out I know that for sure!

Scud

 

[Hoomgar]

Scud, your exhaust gaskets should look like this:

Little rings. Usually with an asbestos like material in them.

 

[Scud]

Hoomgar,

hmmm..I had nothing like that on my exhaust pipes, mine were as mentioned only the outside pipes had half moons that kinda made a complete circle where the pipe went into the manifold and they were steel wtih no asbestos type coating on either of them...just plain steel.

Does Dennis Kirk have them do you know???

Thanks,

Scud

 

[Hoomgar]

The gasket sits in the head and the end of the pipe is pressed into it by the clamps. It sounds like your describing your clamps. Look into the area where the pipe end fits into the head and you should see your exhaust gaskets in there. They can be worked out with a small screwdriver usually.

Dennis Kirk may, or Bike Bandit or just get them from mostly any motorcycle shop or the dealership. Also on eBay all the time.

 

[gsBert]

yo dude!
you dont do a plug chop at various rpms, you do iy at various throttle openings, 1/8, 1/4, 1/2 and full.

and those tubes the needle slides in are called emulsion tubes or needle jets.

your petcock is vacuum activated, so follow the hose from your petcock. it plugs into one of your carbs (the small hose not the fuel line). make sure the other carbs have plugged nipples (nipple being the piece of metal the hose connects to) if your #1 cylinder doesnt have it pluggued, then theres your vacuum leak.

if your #1 goes to the petcock and your petcock doesnt flow on ON (ie you have to drive on prime or reserve or always flows on ON (ie even with the engine off), your petcock diaphragm might have a tear which would lean out the mix in that cylinder...

ill say more when i think of more

 

[Anonymous]

Hoomgar,

hmmm..I had nothing like that on my exhaust pipes, mine were as mentioned only the outside pipes had half moons that kinda made a complete circle where the pipe went into the manifold and they were steel wtih no asbestos type coating on either of them...just plain steel.

Does Dennis Kirk have them do you know???

Thanks,

Scud

Scud,

You should have those four 1/2 moons and 4 gaskets. Mine were stuck in the manifold and I didn't get the old ones out (forgot to do it) and installed the new gaskets and then had to pull the pipes off again to take the old gaskets out. Get in there with a small pointy tool and get those old gaskets out.

 

[Scud]

Cracker, I looked into the exhaust ports and they must have fallen out or been removed prior because they are not in there...I went to my local Suzuki dealer and ordered four OEM gaskets at $4.29 ea. Should be here about the same time my new exhaust system arrives. There is a ton of carbon in each of my exhaust ports, id ther something I can do to remove all that carbon right now???

Gsbert, yea, your right and I understand now, it is the THROTTLE openings..gotcha!...also, thanks for the terminology..emulsion tubes. I will pull those and make sure all the holes are clear.

My petcock goes where you say it does and all the others are indeed plugged at the nipples. and you bet...when you think of more let me know, I really, really,really appreciate all the info.


Scud

 

[gsBert]

scud: so? does your petcock go to the #1 cylinder? did you check to make sure your petcock only flows in the PRIME position? and flows under vacuum in the on position?

if not then you have a busted petcock diaphragm and that's your vacuum leak at cyl 1...

unlikely but worth a shot

 

[Scud]

gsBert, The petcock hose goes to the number two carb, the others do not have any kind of nipple on them at all in the location where it attaches to the number two carb.

I did have the petcock apart last year and cleaned it out, the rubber diaphragm was fine at the time.

Thanks!

Scud

 

[Hoomgar]

No exhaust gaskets!?!?!?!
Cracks and holes in the pipes?

I'm putting money on 90%+ of your troubles being related
to your exhaust setup.

 

[Scud]

Well.....I sure hope so it is starting to get expensive!!

Scud