Compression problem

[TopCatGr58]

Hey Brian,

I'm surprised the bike even started with those carbs!
BTW I editted your post so that the photos would show in the post, when you go to photobucket, copy the last popup link the photos shows which is the one with the IMG tags around it, and then paste those links, hit return to put each picture on a separate line. You don't even need to use the IMG insert button, just paste the whole LINK with the IMG tags just as they are.

Now, take some photos of the broken float post, depending on where it broke will determine the ease or complexity of the repair, they can be repaired often fairly easily and much cheaper than trying to get a spare body or bank of carbs. Take the float post PIN and sand/file/emory treat the shaft near the head to narrow the pin so that it will easily slide into the float posts WITHOUT needing any pressure...they do NOT need to be a snug/ interference type fit, the float bowls will keep the pins in place.

Cudos at getting the pilot jets out in 1 peice without breaking off the brass slots!!! Pull the vacuum slide caps, take out the slides, and then GENTLY push the emulsion tube...the MAIN JET NEEDLE...the brass tube that the main jet was screwed into. There is a PIN and slot in the end of the tube and carb body so that's why care is needed to push them up to get them out of the carb body for soaking and cleaning....the part...not the whole carb body. You do NOT want to soak the bodies in caustic carb cleaner.

Follow the directions in the tech tips for cleaning the carb bodies. In the collection of parts you showed, you did NOT show the Pilot jet needle, they are hidden under brass or aluminum caps on the top front of the carb body where they fit into the intake boots. I think the tech tips describe how to carefully drill into and remove the caps so you can access the pilot screws, necessary for proper cleaning of the pilot circuit, as well as tuning later! There are small metal and rubber washers on the ends of the pilot screws, be careful removing them..again see tech tips!

Looking forward to seeing the photos of the broken post!

T.C.

[skids]

(snip)
Just an update so far. The carbs are not leaking now the bike cranks and idles low for a couple minutes while I tweek the throttle to keep it running. then it picks up and idles high for about 5 to 10 minutes then idles way back down and wants to die again. And it seems to be running rough.
.

It may be that the carbs are running a bit rich on the low end rpms. Once the engine is running normal temp, color some clean plugs near idle (even if you need to hold the throttle to get 1500 rpms.) Running rich can be float heights, wrong pilot jets, mixture screws or synchronizing carb vauccums (the last two would show some plugs out of wack, but not all). Of course, leaking floats will affect some of the float heights and if you are not using a stock airbox, you can't plug the breather hoses - this is only relevant to the older carbs because 80 and 81 carbs vent through the inlet bells. Not also that filthy filters will cause an over rich condition. I like to use a spray bottle to see which head pipes are not sizzling...

[skids]

OK, I read through the rest of the thread. Yeah, clean those carbies. I would go with ultrasonic cleaning and follow up with spray cleaner!

[cywelchjr]

I agree. Older carbs and newer (plastic) floats means there is something that has been changed that we do not yet know. We need to know what he is working with before any solid advice can be given. Appears to be older carbs does not quite cut it. Do a search on the carb differences and maybe take some pictures of what you have so we can respond appropriately.

If the needle valves have o-rings, and being that it's an 80 unless it's been changed they are either the hybrid carbs or the new style (the only difference would be the rubber plug being needed, the are the same other than that even the jetting for some reason).

From what I've seen so far, the hybrid carbs, at least on these bikes are rather rare, although I have them on my XS400, with brass floats even

[cywelchjr]

Brian, those carbs definitely need some serious cleaning!
As far as the smoking less now, that may just be the rings getting broken back in. You may find that your compression numbers are getting a little better now.
The backfiring could also be because of a too lean condition. By the look of those carbs, if they're not suppling enough fuel then you'd be too lean.

As far as the 1980 carbs, I've got a G and a SG and my G has the crossover hole and thus the plugs in the pilot jet, while my SG does not and no plugs.
Your pics show no rubber plugs there, so I'd assume you have no crossover hole, but the only way to be sure is to look once you get those emulsion tubes out.
I didn't see the #4 float post broken in the pics. Is it the pin or the support post?

Also when you go to break those things down for the cleaning, make sure you pull the idle mix screws out too. Check the tech section here for the carb cleaning 101 thread/post/sticky.

If the rubber plug is needed and is missing it will hardly run at all off idle, as it will bog as the main circuit will get fed unrestricted fuel without going through a jet as with no plug that passage totally bypasses the jets to the main circuit DAMHIKIJK. Unfortunately you have to be able to take it on the road to tell cause you can't really hit the mains just sitting there.

[Rasputin]

If the needle valves have o-rings, and being that it's an 80 unless it's been changed they are either the hybrid carbs or the new style (the only difference would be the rubber plug being needed, the are the same other than that even the jetting for some reason).

From what I've seen so far, the hybrid carbs, at least on these bikes are rather rare, although I have them on my XS400, with brass floats even

Hey at least we ended up with some pics...Those tell a thousand tales. Yes I missed that until shortly after I posted the I hit my head against the wall in disgust. Those O-rings may them selves be the cuplrit but until those arbs are cleaned we will never know.
I thought and I will check back that he said they had been cleaned and the float hieghts set. Unless he knew which carbs he was dealing with how would he know what to set them at? Not knowing what set of carbs you are dealing with will cause no end of problems.
That said I stand by my post.

[B.B.]

Hey guys thanks for the posts. Sorry I have been gone to church camp for a week but i am ready to get these carbs figured out. I removed the emulsion tubes and there is no hole that runs to the jet port. I cleaned them up and need to fix a few things.

The post- I took a pic maybe you can help me with or replace the whole carb body.

the tip of the needle is broke off. Not sure what this may causeor were I can replace it. Also has a small tear in the rubber boot. All this on #4 carb. Not sure why?

This is a small rubber washer, and I am not sure were they go can someone tell me?

[B.B.]

TC thanks for the help with posting pics. Hope this helps you guys help me.

[B.B.]

Carb rebuild

Need to go ahead and rebuild the carbs. Can I get some Advice?

Can some one tell me if this is the right kit for these carbs? found it on ebay for $75.00. Also is the price about right or not?
1343532422/**http://www.ebay.com/itm/4-YAMAHA-1980-XS1100-SG-SPECIAL-CARB-KITS-XS1100SG-/360437994651

Not sure if I posted this right. It says it comes with this!
BRAND NEW PREMIUM CARB kits for 1980 XS 1100 SG SPECIAL

EACH KIT INCLUDES 120 & 125 MAIN & 42.5 PILOT JETS

I also throw in 2 x 110 jets to get bikes back to OEM specs

You are bidding on a set of 4 kits. THESE KITS COME WITH ALL GASKETS AND O-RINGS, IDLE MIXTURE SCREW, MAIN AND PILOTS JETS, FLOAT NEEDLE AND SEAT ASSEMBLY.

Any Help is greatly appreciated.

[jwhughes3]

Brian,

Those are the correct sets from Georgefix.

I personally would not order the kits till you get the body fixed or replaced.

You can take float pin and broken post to be TIG welded if you cannot do it yourself.

Does not seem other methods last on post. If it cant be fixed you may wind up pickng up a different set is why I said wait.

If you know for sure you are stickng with the 80 carbs even if you replace that body, then go ahead and order.

Small rubber washer goes with mixture screws and topped by very small metal washer.

The diaphragm can be repaired with rubber PlastiDip Electrical Tape. Brush on both sides of tear and allow to dry overnight.

New needles for slide can be ordered online.

John

[BA80]

All you really need is float bowl gaskets and float valves. Jets don't wear out and most aftermarket jets are wrong anyway.

Find some po' boy kits that have just the gasket and float valve. That's all you need.

[motoman]

Need to go ahead and rebuild the carbs. Can I get some Advice?

Can some one tell me if this is the right kit for these carbs? found it on ebay for $75.00. Also is the price about right or not?
1343532422/**http://www.ebay.com/itm/4-YAMAHA-1980-XS1100-SG-SPECIAL-CARB-KITS-XS1100SG-/360437994651

Not sure if I posted this right. It says it comes with this!
BRAND NEW PREMIUM CARB kits for 1980 XS 1100 SG SPECIAL

EACH KIT INCLUDES 120 & 125 MAIN & 42.5 PILOT JETS

I also throw in 2 x 110 jets to get bikes back to OEM specs

You are bidding on a set of 4 kits. THESE KITS COME WITH ALL GASKETS AND O-RINGS, IDLE MIXTURE SCREW, MAIN AND PILOTS JETS, FLOAT NEEDLE AND SEAT ASSEMBLY.

Any Help is greatly appreciated.

Well, for starters, the main jet size in those kits is totally wrong. The 80-81 Specials used 110 mains ALL across the four. So, with that, it is unlikely that any of the jets are Genuine Mikuni anyways. 99.9% of these 'kits' do NOT have Genuine Mikuni jets in them, aside from them not even being Mikuni. I know they sure sound the convenient route, but guarentee you'll be back here with stumbling and running issues. If not torn, I'd use the original bowl gasket, replace the float needles and seats, clean the pilot and main jets, replace if not 42.5 six-hole variety pilots and 110Mikuni mains having the Mikuni swirly logo.Do NOT use metal pins, paper clips, etc., to clean holes on jets. A toothpic is tool of choice. Those jet sizes are specific to 80-81 Specials with stock exhaust and stock intake box even if using a foam or K&N filter. Hope that helps. BTW, float levels are measured at highest point of float, with 23mm being the setting, key is IDENTICAL setting for all eight floats.

[jwhughes3]

Brant don't you think its unlikely he will have to replace his main jets, they are too easy to clean...its the pilot jets that he will likely use from those kits. At least if it was me thats all I'd use besides the orings and gaskets and valve needle sets.


John

[motoman]

Brant don't you think its unlikely he will have to replace his main jets, they are too easy to clean...its the pilot jets that he will likely use from those kits. At least if it was me thats all I'd use besides the orings and gaskets and valve needle sets.


John

If not Genuine Mikuni pilots, still would NOT use them, correct holes or not. Same goes for the mains. This, as you know is one 'good enough' short-cut you'll regret forever and NEVER get the scoot to perform flawlwssly......unless corrected..... DAMHIKIJD.

[B.B.]

OK so after reading the posts. Is the Float post fixable and if so then how?

Also Moto do you think I should replace the float needle and seat?

Last, what is the difference between the xs1100E, xs1100L, xs1100S, and what would I need. I am looking at replacing the float needle and seat, and bowl gasket. Thats it, none of the jets.