First Ride Report

[skids]

Rob, unless the diaphragm leaks fuel into the vacuum line, you should be able to do something real easy to check out your theory. That valve that you spoke of is an air check valve (one way valve) with a restriction in it, I assume it is to help prevent oscilating movement of the main diaphragm. If yours is malfunctioning, two cylinders would be fuel starved. Switching to prime would instantly tell you if that is the problem, as it would begin firing all 4.

[skids]

PS, that check valve can be removed for inspection (at least I have done it).

[79XS11F]

That valve on mine appeared to be crimped into place but I will check it even more closely next time i have the petcocks apart.
What I noticed was that sometimes at ANY petcock setting no fuel was leaving the petcock ( and yes there was enough fuel in the tank) I Also noticed that sometimes fuel also flowed at any setting. In both cases blowing and or sucking on the vac line would cure the issue so I was guessing that one way valve might be sticking.
On another note when I checked my vent lines by blowing into them fuel squirted out of the pilot jets? on the carb mouth rim on the air box side of the carbs. Would that be a normal expectation?
Rob

[skids]

I would say "yes." As you pressurize the space above the surface of the fluid, it will force fluid out of the carb any way it can go. The main jet is slightly submerged, so gas comes out the main jet and the pilot jet and possible other places.

It does sound as if you have a sticky petcock valve.

Originally posted by 79XS11F
On another note when I checked my vent lines by blowing into them fuel squirted out of the pilot jets? on the carb mouth rim on the air box side of the carbs. Would that be a normal expectation?
Rob

[Ken Talbot]

Originally posted by skids
That valve that you spoke of is an air check valve (one way valve) with a restriction in it, I assume it is to help prevent oscilating movement of the main diaphragm.

That d@mn little check valve is the main reason petcocks leak on a standard. It "traps" the vacuum so well that when you shut off the motor, the residual vacuum on that side of the diaphragm is stronger than the spring force trying to close off the petcock. Wallah - you've got gas flowing when you don't want it. Take a stiff piece of wire and poke a good hole through it, and you will have no more residual vacuum problem. When you test the petcock operation, you will see the fuel flow snap off as soon as vacuum is released. That's how you want them to work. I did this to all of my standard petcocks, and to the equivalent part on a special octopus, and I've never had a problem since.

[79XS11F]

OK ... but does that little valve prevent fuel from flowing through the vac line as a fail safe?
Rob

[Ken Talbot]

That side of the diaphragm is dry. The orifice only applies or releases vacum. If there is gas on that side too, then the diaphragm has a hole and needs to be replaced.

[79XS11F]

Fair enough .. I will "fix" that little bugger this weekend.
Rob

[79XS11F]

NO head re & re necessary

I just finished taking the compression readings and they are good enough for me so NO HEAD RE & RE will be necessary this weekend.
Readings:
#1 = 143
#2 = 150
#3 = 153
#4 = 153

The plugs are off white on the tips and damp black on the bases. Insulators are dirty white.
SO now I am a little confused about what is going on. She still buzz's and or shakes and I feel that she lacks power as in a mis fire. It must be intermittent based on no single plug looking real BAD. They are all pretty close to one another in appearance.
I am going to guess that the issue is the fuel petcocks. I am going to guess that the engine is sometimes fuel starved. So I am going to puncture the one way valve and also run some sea foam through the fuel system.
Keep you posted
Rob

[79XS11F]

I got my fuel petcocks working and took my bike out for a 50 mile run early this morning. She is pulling strong and handling well but the "buzz" is still there. I will guess this is an engine mounting issue and will check it out the next time I service her. I did notice that there is mild popping in the stock exhaust which is odd given that the carbs are set up for stock. Perhaps I should turn the idle jets down. I started them at 1.25 turns out from lightly seated before putting the factory adjustment limiters on them.
OH .. I also painted and rebuild a pair of factory rear shocks using NOS OEM springs this morning. They cleaned up nice and that makes this bike complete except for the matching paint on the side covers and tank.
Rob

[79XS11F]

I BEAT her last night and she didn't die

I was out last night putting another 50 some odd miles on my bike and I decided to give her a beating to confirm that she would in deed stay together. She took the beating well and in fact LOVED it. She pulls very strongly to red line and is idling reasonably smooth. The buzz however remains and is directly related to acceleration. At 4 to 5 K she is GOOD below that and above that the buzz makes her a handful and the harder the throttle is turned the more she buzz's but will calm down a bit once any given RPM is maintained.

About this BUZZ ... Could it be the end result of the assembly order? You may remember that I torqued the engine in before the swing arm was installed. Manual indicates that if engine is replaced that the finial drive flange should be torqued before the engine. Perhaps I should back off all the engine and flange bolts and torque them again doing the swing arm flange first.
Rob

[TopCatGr58]

Hey Rob,

IF you are talking about the 4 bolt/nutted flange that secures the final drive assembly to the swingarm, then I don't believe it makes any difference, cause many folks have done a final drive swap out, and have NOT loosened their engine frame bolts to do it!

But if you are talking about the swing arm pivot bolts, then that might be different, since they are going thru the frame, and doing them first, THEN tightening the frame/mount bolts may have shifted the frame changing the torque on the drive shaft pivot bolts?? JAT??

Still think it's either exhaust rub or frame mount bolts/bushings, but will be curious to find out what it was once you figure it out!
T.C.

[79XS11F]

Hey TC . I was talking about the 4 final drive bolts. I just know that in my manual it says that when replacing the Engine that the flange bolts should be torqued before the engine bolts. that is of course based on the swing arm having not been removed. With with my bike rebuild I put in the engine and torqued it in place before the swing arm was installed. I centered the swing arm as per the manual and managed to get it perfectly centered. The bike tracks real smooth and nice so I am content with the swing arm placement. Now given that the connection is made through a U-joint it really shouldn't matter.
I am using the same engine mounts as was on the other engine and I did not have this issue with that engine so your likely right. It is likely a engine mount / torque issue.
Rob