Clutch slipping - synthetic oil?

[Georgboy]

I have just bought a 1979 xs1100 and I have a few questions on it. First I am having a small skip on the number 1 carb if you take the vaccum port cap off it runs fine but with it on it had a skip. Second the guy before me has ran 20w50 synthetic oil and if you get on the bike the clutch slips, is that the oil causing it to slip? Where can I get a 160 mph speedometer and cable? Thanks alot for the help guys. If someone could call my number is 706-474-2984 thanks jeremy.

[Ivan]

there are some that swear that synthetic will cause clutch slippage, however I have not found that to be the case. There are several tech tips that give advice on putting in an extra clutch steel, clutch adjustment and such. Look into those, and see if it doesn't help.

[cueball]

Was the synth for cars or for bikes. Car oil with friction modifiers will cause clutch slippage in bikes, cars run dry clutch, bikes wet.

[TopCatGr58]

Hey GeorgBoy,

Well, first welcome, congrats on your machine. Secondly, carbs are the #1 problem people encounter with getting old used machines. Removing the synch port cap should severel lean the carb, reduce it's ability to draw fuel thru the pilot circuit. So....the carbs are probably not right, and a good disassembly and cleaning is probably in order.

You'll want to make sure that the vacuum advance hose is connected to the proper place..the metal port on the #2 carb body, not the intake boot port!

The #2 problem is electrical, and the pickup coil wires are the #1 of that, followed by a falling apart fuseblock, corroded connectors, etc.!

With the synch/vac port open, it may not be getting much if any fuel thru # 1, and so there's nothing there to fire...much less misfire, whereas with it capped, it's trying to draw fuel, but the pilot circuit is easily clogged and so again, it brings us back to a cleaning of the carbs as job/priority 1!

The 79SF should have come with a stock 160 mph speedo. Yours may be broken, don't know, you didn't say? Ebay is one place to find these parts, but these are rare and $$. An Xsive on here Andreas Weiss, provides lots of quality used parts at much better prices than ebay, but again this is a much sought after part, so he may not have any??

You can get aftermarket, but the ones on Mikesxs.net are a bit smaller than OEM! You can use any XS series speedo, 650, 750, 850, and they vary from 120 mph, 140, as well as 160. These machines top out at 130 if you're lucky and have the cahones to take it that far, otherwise, anything over 100 isn't really used much! The cables can be gotten from your local dealer, or ebay, or bikebandit, and there is a difference in the way the cables attach to the speedo drive gear at the wheel on your special vs. standards!

Doh..forgot to talk about the clutch! Short answer, if clutch is already near the point of failure and slippage, then synthetic can contribute to it slipping. Folks have gotten reduced slippage when switching from synth to dino. Others have stated, with new clutch parts, synth works fine! YMMV!

T.C.

[Silent]

My '79 Special runs just fine on the original clutch plates and full synthetic 15-50 (Napa automotive oil, no friction modifiers). I did install HD springs tho. That might be something to check into if you're slipping.

[Georgboy]

the exhaust going into the number 2 cylinder wiggles. I cannot get it to tighten up completely. I tightened it a little to tight and the stud broke off in the head. How do I get the pipe to tighten up? New crush gaskets?

Let me get this right the cable is going to attach different at the wheel or the speedometer? What kind of hypoid gear oil are most of you guys running in your final drive? Will a speedometer be accurate off of say a 650 or 750 bike ? Thanks guys

[TopCatGr58]

the exhaust going into the number 2 cylinder wiggles. I cannot get it to tighten up completely. I tightened it a little to tight and the stud broke off in the head. How do I get the pipe to tighten up? New crush gaskets?

Let me get this right the cable is going to attach different at the wheel or the speedometer? What kind of hypoid gear oil are most of you guys running in your final drive? Will a speedometer be accurate off of say a 650 or 750 bike ? Thanks guys

Most likely the crush washer is actually missing, but yes, that's where I'd start. IF the others can be tightened, then it's not a mismatch of pipe to bike, some were made to fit specials vs. standards, and they have different stud lengths, the flanges stuck out away from the head more on one vs. the other, but this doesn't sound like what you have since the others can be tightened. You can get a pack of 4 fairly cheaply from several sources, PNM for 1.

Yes, the speedos will be accurate from any of the XS series bikes, and the cable fitting is different at the wheel drive gear on specials. ANY synth 80-90 hypoid gear oil will be fine in the middle and final drives, there's no CLUTCH there!
T.C.

[trbig]

When you get that stud fixed, it doesn't hurt to double up the exhaust crush gaskets.


Tod

[Georgboy]

What size jets?

I am going to be rebuilding the carb this weekend and I have the stock headers (2into1) exhaust but with harley mufflers welded on the end ( bought it that way LOL). What size jet do I need to run? Who makes a strong holding clutch for these bikes? Thanks guys .

[Georgboy]

I forgot to mention I have the stock air box also.

[CatatonicBug]

Who makes a strong holding clutch for these bikes?

Not sure what you mean... You already have the best clutch for these bikes. It's so good, that Yamaha continued to use it on all their bikes, up to the present day. You don't need to replace it. As mentioned earlier, you can add a steel to the stack of plates, and I've heard some people needing to sand the glaze off of the existing ones. Also, new clutch SPRINGS can help. Start with the springs, then if that doesn't do it for you, add a steel.

[madmax-im]

No Moly!

One thing about synthetic oils...they come 2 ways...with Moly or without Moly...If you see on the oil"can" a label that says "energy conserving" then you dont want that one it contains Moly...in a wet sump clutch moly will cause it to slip thus it should be avoided...since you do not know what exactly the PO used...I would flush all the old oil out and refill with the right kind....

[Georgboy]

what size jet?

Should I up the jets at all or leave them stock due to the exhaust?

[WMarshy]

If I were you, I would start with the carb cleaning and forget about changing jets for now, it shouldn’t be needed. I run a 4-1 header with everything else stock and I was able to get my bike to run very well without changing any jets. I had a discussion about adjusting carbs and which method is the "best" but it’s open to interpretation. Feel free to read through this, you might want to check float height and maybe adjust the needle height eventually...? Good luck and welcome.

http://www.xs11.com/forum/showthread.php?t=23195

[MindWebs]

stock jets are fine, i'm running them on my xs11sf with 4-2 and harley mufflers
ebay, seller georgefix has your carb rebuild kits $74 with shipping (4 kits)

why run synth? nothing lasts forever. it's called engine rebuild 101.

to each they're own.. Good luck!!!