ignition advance springs

[supercooper04]

Hi,

Out riding the bike after a strip down and rebuild, engine was left. I have replaced the points, coils, resister, HT Leads and put new plugs in. Set the ignition timing and checked with the light. Took the bike out for a spin and for the first 5 miles it was spot on. Then it seemed to go to 1 cylinder and wouldnt pull away or rev up. On idle seemed OK and was running on two. Pulled the plugs and have a spark. I have an idea that the timing may have slipped. But just before I start to check this can anyone give me crash course on the advance retard springs. I have taken off the cover and the springs are pulling the arms in towards the shaft. Pull the arms out and they stay there. After reading a few posts they should return, Is this correct and do i need to check anything else. and is there a method of striping it down and rebuilding. I cant find anything in the Haynes manual.

Cheers, ken

 

[osteoderm]

The springs and flyweights should snap back to center. Watch this vid for clarity:

http://https://www.youtube.com/watch?v=sgofxl6Adx4

The exploded view of the relevant parts is on page 45 of the Haynes manual. Part #6 (ATU shaft) is probably binding on the bearings (Part #2).

 

[supercooper04]

Ta for the link , couldnt find it when i looked earlier. What would be the symptons of the bike if the weights were stuck open ?

 

[osteoderm]

Timing/advance could be your issue, but some of the symptoms you're describing could also be fuel-system related. In any event, it would be pointless to continue troubleshooting things until you have the advance working smoothly/properly and have verified the timing and advance action through the RPM range.

 

[Austblue]

I'd suggest that if you have the funds buy Pamco Pete's electronic advance rather than playing around fixing the springs.

 

[wherearewe]

Might need to give the assembly a bit of a clean up or the springs could be shagged. Try this:

http://www.xs650.com/forum/showthread.php?t=18187

and here is another good link

http://hughshandbuilt.blogspot.co.nz/2012/05/how-to-pamcopete-277-ignition-install.html

See how that works out for you.

 

[Tomterrific]

One bit of minutia to recognise is the drag on teh points cam from teh points heel. The drag will hinder the advance from retarding all teh way even if it is working fine. Likewise, teh drag while the engine is running will help the advance retard.

Tom

 

[supercooper04]

Right, Just done the following, Stripped and cleaned the advance mech and rod. Shortened the spring buy one curl. And they know snap back in position. One thing worries me, I have read that there is bit of paint on one arm and one on the sleeve. Thats not on mine so does that really matter.
The bike is doing the same as before and missing and just running very rough when trying to ride down the road. plugged in the timing light and the rotor was running between the T marks
I made some calls today to try and source some throttle sleeves on the carbs as mine are a bit worn (very difficult to get bits in the UK) Talking to the carb man about buying other bits n bobs and explained i was running BS38 without the airbox just Ram Air foam filters. He said that the carbs would be running all other the place and wont work when under load from the engine. He has recommended VM34's.
Before i go down this route I want to be sure he is right, anybody got some advice on this. Thanks again
PS the cylinder pressure was 165

 

[TwoManyXS1Bs]

Hey supercooper04, need to rethink those advance springs. The spring tension defines the advance curve of your timing. Too much tension and you'll be running retarded, motor could overheat. Your bs38 carbs have a respectable performance if in good shape. JBindustries.com has come to the rescue with replaceable diaphrams and spigots (brit term for carb holders?). A lot of your answers are buried here in this forum. Try forum searches on: 'bs38', 'jbindustries', 'carb tuning'...

 

[wherearewe]

Hey supercooper04, need to rethink those advance springs. The spring tension defines the advance curve of your timing. Too much tension and you'll be running retarded, motor could overheat. Your bs38 carbs have a respectable performance if in good shape. JBindustries.com has come to the rescue with replaceable diaphrams and spigots (brit term for carb holders?). A lot of your answers are buried here in this forum. Try forum searches on: 'bs38', 'jbindustries', 'carb tuning'...

There are many people who modify their springs but still have acceptable advance function simply due to the fact that they stretch with time - within reason obviously.

Damn i had some brand new OEM springs on a brand new OEM advance assembly be too soft! Age maybe? Who knows.

Usually you would only trim one spring. Do a timing check and make sure that the timing is coming on in a nice smooth curve as you rev up to about 3500rpm, by then it should hit full advance but not go past. If it goes past, you have a whole another problem with worn ATU stops and weights and i would get one of Pete's new units.