Clutch Always Out of Adjustment When Engine Cold

[jmd_forest]

On our recently completed cafe racer, upon startup when you pull in the clutch and shift into first gear the bike lurches forward and dies without ever letting out the clutch. I adjust the clutch using the cable adjustment at the hand lever, little by little until it stops lurching forward. At this point when you shift into first and let out the lever, the clutch will not engage. Then I adjust it back to "normal" again and I'm back to the lurch forward and die without ever letting out the clutch. A few cycles of this and the clutch eventually will engage and disengage and I eventually wind up with the cable adjustment in essentially the same position as when I started and the clutch seems to work fine until the bike is cold again.

The cable is fine, not worn or frayed anywhere. I initially adjusted the clutch using the port on the side of the engine, and have resorted to using that once or twice when I couldn't get enough play in the cable adjustment at the lever.

One possibility I'm checking into is the routing of the cable and overall movement of the cable when cold but the cable seems firmly seated in the cable ends throughout this strange adjustment period, cold or warm. I did install clubman bars but retained the original cable that came with the bike while routing the cable with nice flowing loops (no tight kinks) to take up any slack.

Any ideas?

 

[DanMach]

Have you tried starting it in neutral and letting it warm all the up at idle before shifting? Thinking some kind of oil thickness dealie...

 

[jmd_forest]

I'll give that a whirl and let it fully warm up before first shifting into gear. Although I don't think it will matter, it can't hurt to try.

 

[lhaolpa]

What kind of oil do you use? Too thick oil will allow the clutch to drag until warm. I use 15w40 diesel type oil,as it has zddp additive,which works well with wet clutches,and also protects the bearings,gears,etc. It will also start out 15 weight when cold,then change to 40 weight when warm. lha

 

[jmd_forest]

I'm using 10W30 conventional oil. I understand the clutch dragging but can oil drag really enable a very stiff lurch forward and stall of the engine upon shift into 1st? After the stall, with the clutch still pulled in, I can't even move the bike until I shift into neutral.

 

[dburrows6735]

Is that 10W30 a motorbike oil or car oil? There is a diffrence.

 

[jmd_forest]

It is conventional car oil. Conventional means no extra lubrication additives that would cause the clutch to slip but also no zddp. However, unleaded gas in US started in 1975 so I assume our 1980 had valve seats and cams conducive to unleaded fuels. Regardless, I would expect "slippery" additives in modern oil to have the opposite affect than what we are experiencing.

 

[bentwrench]

Hate to say it, but it sounds like that beautiful bike is messed up.


Of course, I'll take it off your hands for a nominal fee...

 

[lhaolpa]

Have you adjusted the clutch at the transmission end of the cable? Look at your manual to find the right method for your model,and check it out.You have to find the right point where it's tight enough,but doesn't slip or grab. Good luck. lha

 

[jmd_forest]

Iha,

Yes, I have adjusted it several times at the transmission end of the cable, per the manual, with the same results: after finally getting the adjustment "right" you can ride all day without any problem, no slip, no lurch. Next morning ... BIG lurch forward and stall when shifting into first and then adjust in, out, in, out, in, out ........ and wind up essentially back where it was yesterday when running correctly.

Bent,

<sarcasm>
I'll even throw in a few bucks for you to take it off our hands. Thanks.
<end sarcasm>

Seriously, this is just one of a few bugs we're working out on our recently completed build but since my son is a new and inexperienced rider I don't want mechanical issues distracting him while riding.

 

[OliverB]

Thoroughly warm up the engine. Drain that oil and also clean out or replace the oil filter. Car engine oils, other than a few special types such as diesel grade, should not be used in wet clutches. They can cause the clutch to drag more than usual. As Iha said, get yourself some diesel grade, name brand 15W40 oil. I prefer valvoline Blue (Premium) as it contains about the most zddp, short of racing oils. BTW, this oil was designed for hard working engines - both diesel and GAS! After installing the new oil, it will take a while for the clutch plates to get rid of that auto engine oil and saturate with the new oil. Don't expect an immediate difference.

Adjust your clutch play at the engine as described in the service manual and set up the brake lever with the proper amount of free play. As you may already know, on a cold engine, it is perfectly normal for there to be some lurching when you shift from neutral to first. The lurching lessens when the oil is hot but never goes away completely. Our clutch is a multi-plate design and is immersed in oil so there is always some drag even when disengaged. However, there should not be so much drag as to make your engine should not stall out. Is your engine set up properly in terms of idle speed and carb settings and function?

 

[HoughMade]

I may completely off base, but it sounds like the locking nut (jam nut) at the clutch pushrod adjustment is not locking the adjustment down. Whenever I go to adjust the clutch, which is not that often, that nut takes a lot of force to get loose- and I mean a lot.

Just a thought.

 

[jmd_forest]

Since I have no other good possibilities, I'll change the oil for some 15W40 diesel oil but I find it unlikely that the oil could lock up the clutch enough to lurch and stall the engine (a damn strong lurch that I need to control with the front brake) .... but oil is cheap and easy to change.

HoughMade,

I believe the nut is locked pretty well since 1) I am locking it down myself with pretty decent force and 2) once the clutch starts "working" the cable adjustment by the lever is in essentially the same spot as before the adjustments. But, I will ensure it has not come loose.

Thanks for the suggestions and I will keep the thread posted

 

[jmd_forest]

Ok ..... started up the bike and let it warm up fully and surprise, surprise, no lurch. It must be the oil drag. Hard to believe oil drag can cause such a strong lurch. I guess tomorrow is change the oil to 15W40 diesel oil.

Thanks to all for their help.

 

[DanMach]

WOO YA! I NAILED IT!

(Also congrats to you)

 

[jmd_forest]

It happened again today but just the opposite. Went for a nice 20 mile ride early this afternoon. Clutch and shifting went smooth from initial startup to the stop for lunch to the ride home. This evening, after about a 4 hour cool down, started the bike, shifted into first and tried to pull out of the driveway and the clutch would barely grab. Adjusted the clutch via the nut and screw on the side of the engine and clutch was working fine again.

I have looked at the routing of the cable and as far as I can tell, no kinks or tight corners that would hang up the cable and the cable is zip tied to a frame member under the seat near the battery to help eliminate any play that there might be.. During the rebuild of the bike I did have the side cover off and cleaned and relubed the clutch actuating mechanism and tightened up the butterfly return spring in the case but it all appeared to work smoothly upon installation. I have not changed the oil since it had been working correctly for the last week although it didn't get much use due to weather.

If I can't figure this out I'll be carrying a 12mm socket and philips every time I ride.

I'm a half decent mechanic and I'm at a loss.

 

[lhaolpa]

That may take a while to settle out,as the clutch plates absorb the oil and may take a while to change new to old oil and vice versa.You might have to live with a little bit of adjustment now and again before it rights itself. Many bikes have the problem of grabbing of the clutch when the oil is cold. lha

 

[FUBAR]

maybe swap out the clutch disks and springs, its not too pricey. but i agree with everyone saying oil. i have heard of this before. i use 20-50 diesel grade

 

[jmd_forest]

Well, since the consensus seem to point to the oil, I got a gallon of 15W30 diesel oil yesterday and this weekend is change the oil weekend. I hate to throw out the $10 of basically new oil already in there but this is the only way to confirm or deny that the oil is the problem. I'll keep the thread posted.

 

[XSLeo]

FUBAR, 20w50 diesel, must be something special. We can't get that around here. The Dino oils are 30w or 15w40. Some of the synth oils are 5w40 but not 20w50. What brand and where do you get it?
I have found the way the book describes the clutch adjustment in the side cover to be a bit loose. Where it says to tighten till you feel resistance and back of 1/4 turn is too much. 1/8 turn works better.
Leo