Main Jet Dirt, Slipping Clutch, and a Gas Leak. What a Weekend!

[jennings2309]

1979 XS1100F has been running pretty well, but it was stumbling as it accelerated from 2K to 5K RPM. Ignition is good, the little wires on the advance are good, starts easy, and runs strong above 5K. But it was just not smooth or making power like they're supposed to do.

Back to basics; checked the float heights and there ranged between 21mm to 29.3 mm, but the book calls for 25.7 +/- 1.0mm. So I set those, and turned to the jets, because I never drifted the main jets out of the center of the carbs.

I placed carb #1 upside down on a clean cutting board and tapped out the main jet. As I lifted the carb body I could not believe my eyes. There, next to the jet was a pile of dirt. Not just a little dirt, but a measurable quantity. I set #1 and the jet aside, scraped the dirt into a bowl and started in on #2. Same result...another pile of Georgia red dirt. Same results on #3 and #4.

All in all, I retrieved approx. 4 cc's of dirt (about 3/4 of a teaspoon!) It's a wonder the damn thing ran at all.

So I put it all back together, hit the starter, and BAM...she revs like a banshee. This is just how my old '81 sounded!

I took her out and got a few neck snapping runs in when, of course, the 40-year old clutch started slipping. Dialed it down a bit and got it home and ordered some new parts.

Feeling pretty good about things, I wandered out to the garage after dinner to admire the ride, and what did I find? Only a pool of gasoline under the bike! Yikes!!

Fuel cutoffs "On"...check. Fuel lines connected...check. So where's the gas coming from?

Pulled the tank and (surprise), two of the the fuel sending unit bolts were only finger tight. I had never checked those. And that was an almost full tank that might have leaked out!

So lets review: Carbs are clean, she's running like a top, clutch worn out, and the sudden fuel leak is suddenly solved.

Can't wait for next weekend.

[bikerphil]

You may want to run some fuel filters, should never have that much crud in there.
Nice you got her running again.

[Ken Talbot]

Just think what it will be like when you follow up with a good sync job! What comes after "runs like a banshee"? ;-)

[MPittma100]

Clutch

If you haven't yet, check both clutch adjustments before you start throwing parts at it. If you are using synthetic engine oil, the clutch will slip.

MP

[Bonz]

If you are already using synthetic oil, and it now starts to slip, the clutch is simply wearing out... If you have a clutch that is worn out or close to worn out, synthetic oil may contribute to slip. A clutch in good repair and adjustment will not slip with synthetic or conventional. 80SG ran great with Castrol 4T Syn 20w50 and it was a 38 year old clutch when I put it in the crankcase for the first time.

Like MP said, check the adjustments are correct at the clutch and the lever. May be simpler than you think, worth doing as a first resort.

[DiverRay]

Replace the clutch springs!!
How old is the engine and clutch? Barnett springs may be all you need. At about $20 and an hour of work, a good first try.

[motoman]

Agree with Diver Ray 100%! Also, use conv. 'dino' oil of the 20-50w variety, not syn! As stated, get that throw-out bearing adjustment spot-on, THEN final adjustment at lever.

[Bonz]

Been down this friendly road and congenial discussion on oil...

Motoman and others are right... Synthetic is not needed in the XS, too short of an oil change interval to make sense $$ wise, but will not make a clutch slip if it is a proper oil for motorcycles in a properly working clutch.

It is not “slipperier” than dino oil, it is simply more uniform molecule size that lets it flow better in colder temps, and not breakdown like the differing molecule size of conventional oil allows for, thus conventional is not as good at extreme hot temp protection, per se.

Running the 2011 Durango Rally on the 80SG, it got balls hot going up Red Mountain Pass from Ouray over to Silverton on the way home. Talking insane hot weather at those elevations (extreme heat, thin air kills cooling at low speed going uphill following traffic). Stopped to take a break and the bike sounded like it had 15w40 conventional oil marbles circulating, and upon start up after the break as well (maybe valvetrain, maybe cam chain, who knows). Back in Durango when we arrived just at dark with cooler temps and lots of down hill running, bike was back to its own happy self. Changed oil upon getting home (always ran a 20w50 after that) but that was an extreme case of oil getting baked. Kinda like the guys going up Pikes Peak for the Canon City Rally’s.

I ran Castrol Synthetic 20w50 4T in my 80SG with not an issue the last oil change before selling it. Don’t understand why would my 40 year old clutch from the same parts bin as all the other XS’s not have the same issue as others that have the issue when I switched from conventional (had the syn Castrol on hand I wanted to use up)? It has to come down to the condition of the clutch, whether adjustment, plates, springs, abuse, etc.

Changing to synthetic if it doesn’t have the same additive package as the conventional it is replacing can cause issues, but it’s not the oil, it’s what is in it and that is up to the owner to understand.

[skids]

I have had issues with slipping starter clutch when using Syn motor oil. To be fair, I have never used Syn motorcycle oil.

[Radioguylogs]

I have had issues with slipping starter clutch when using Syn motor oil. To be fair, I have never used Syn motorcycle oil.

I know I'm getting older, but this doesn't make sense to me. If you never used synthetic oil, how did you have problems with it?

[jetmechmarty]

I know I'm getting older, but this doesn't make sense to me. If you never used synthetic oil, how did you have problems with it?

He used the Energy Saving stuff designed to go in a car. Motorcycle synthetic is a horse of a different color.

[Bonz]

Skids, what synthetic oil was it you had starter clutch slippage problems with? Never heard of that before.

Most any oil that ends in w40 or higher, regardless of MC specific or not, should be free of the friction modifiers that potentially cause slip. Thus the popularity of the 15w40 diesel oils and 20w50 Supertech.

[Radioguylogs]

He used the Energy Saving stuff designed to go in a car. Motorcycle synthetic is a horse of a different color.

I get it now. Thanks.

[skids]

I know I'm getting older, but this doesn't make sense to me. If you never used synthetic oil, how did you have problems with it?

I have never used synthetic MOTORCYCLE oil. I have used synthetic oil. In fact, I also have used a lot of synthetic blends as well.

[skids]

Skids, what synthetic oil was it you had starter clutch slippage problems with? Never heard of that before.

Most any oil that ends in w40 or higher, regardless of MC specific or not, should be free of the friction modifiers that potentially cause slip. Thus the popularity of the 15w40 diesel oils and 20w50 Supertech.

I think it was Mobil 1 (years ago). Multi viscosity and I cant remember those specs but it was not above 40W.