Stella - 1977D survivor, back on the road.

The one I saw was as rough and temporary as mine, but yours is very clean. Worth it for continued use for sure. If only gear selection was as easy to index, eh?
 
Haha, dunno about gear selection, but found speed selection.

ThrottlePosition02.jpg


Was thinkin' about doing a thread on this, maybe to help the tuners...
 
Hey, Hoping those jetting changes make for a fun test ride ! Was wondering if you can convince the wife to go along for a wfo top gear roll on ? I am anxiously waiting for a new jetting combo (5twins formula) test soon also. Cheering for ya ! RT
 
Thanks TM. Yes, main jet testing is a hoot, but I've accepted the fact that it just can't be done safely on my usual commute. I should get a few hours next week when I can head out of town a bit.

The wife? I've asked, but the interest doesn't seem to be there. Maybe one day, but it'll probably be a request for her to drive it herself. She's not one for bumming a ride, would rather be on her own 170cc twist-n-go.
 
DanielBlack said:
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I've taken a closer gander at my tank and tins. Looking at these pics, I noticed the side tin and tank don't quite match in color. They're close (closer in analog reality), but not quite. Further, when you take a look at the decals on the side tin you'll notice the line isn't sharp and the red intrudes on the stripe here and there. A PO has been here before me, the side tins were definitely repainted with the decals taped off. Not too bad a job, really. The rough texture I had thought was sun damage is merely 'orange peel' from the repaint.
 
I regret to report that up until now I have not paid a lick of attention to Stella's gas mileage or compression.

I did the math on the last half tank and it came out to 32 or so. I'm not too concerned as it's way too small a sample and I had been riding WFO testing main jets.

Today I tested compression and I don't believe the results. 75-80psi both cylinders. Kick or starter, engine warm, throttle open. Is it even possible for a bike to run as well as Stella does at such low compression? I got the same results with two testers.
 
Wow - THAT is low. If you do the math....the XS650 has a compression ratio of about 9:1 and if atmospheric pressure is 14.7 psia (except in the White House of course - oooops no politics - my bad) - then you should be getting somewhere around:

9 x 14.7 = 135-150 psi. (for large values of 14.7)

Hmmmmmm. Your numbers indicate some sort of valve or ring problem Daniel. Very odd that good ole Stella runs so well. It makes me wonder if you're doing the test correctly (sorry) but numbers like that usually indicate something fairly dire.

Did you do a "wet" test?

Just put a couple of good squirts of engine oil into the spark plug hole and do another compression test. Simplistically speaking, if the number goes up - you have a piston ring issue (the oil helps worn rings seal better) and if the number remains the same - it is likely valves. If you had a hole in the piston, your number, wet or dry, would be 0 psi, or nearly so and you would have a dead cylinder so the bike would NOT run very well at all.

Again, I say....hmmmmmmm.

Pete
 
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Wow Daniel, I hope that's not really the compression reading. A tear down could be in your future. I also have not yet done a compression test, you got me spooked now, as my bike seems to have every known malady. Good luck and I'll be watching your outcome closely.
 
Fellas, if it runs ok, doesn't make horrible noises and doesn't use a lot of oil.....I'd keep riding it.

As Daniel alluded to - fuel consumption is another indicator of engine condition. My XS650s (the '75 B-model I owned 40 years ago and the '76 C-model I have now) return just about exactly 50 MPIG (Imperial gallon) so that would be just about 40-43 per US gallon, I think. If I run them hard, I get about 5-8% less and if I take it easy, I might get 5-8% more.

Daniel - how about you put a tank through it just riding as normal - and see what you get.

Pete
 
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I fully allow the possibility of not doing the test correctly.

Warmed to operating temp.
Plugs out.
Screwed tester into R plug hole.
Fully opened throttle.
Kicked over to highest reading. 5-6 kicks. ~75psi.
Reset, used starter w/open throttle, 80psi.
Moved to L cylinder, same numbers.

I didn't add oil for a wet test, however the motor had just been running.

Running a full normal-driving tank is exactly what I'm doing. I'll be sure to report my findings.
 
It does sound like you are doing it correctly.

Try the wet test - if it's the rings then the number should jump up a fair bit.

Hmmmmmm.
 
Good sign is your results are equal side to side ! A failure would most likely not be consistent side to side ? I am wondering having never done a compression check on these with CV carbs, how are the slides opening to allow an accurate check ? Seems like the test is giving results from closed carbs ?
 
True TM - that's a good point. I must admit that I also have never done a compression test on a CV carb equipped bike....

....and once again, I mutter.....hmmmmmmm.
 
Well, I don't know the particulars, but the numbers do jump from near zero when I open the throttle. Closed throttle is near zero. Slide must be lifting.

Wet test results: 115L/110R

Edit: These max numbers were reached in 2-3 kicks vs. the 5-6 needed on the dry test.
 
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Ahhhhh....ok.

Well, you may be getting down the road toward a set of rings and a re-bore or at least hone job.

Tell me Daniel, does it use any oil between changes?
 
She does use a bit of oil, but please recall her leaking pushrod seal.

On the last oil interval I had filled to the top of the dipstick range. 1000mi later it was above the minimum by about a quarter of the range.
 

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