Advance Timing Unit and Rod (just to be sure)

[VCPatel]

Friends,

So I got everything adjusted on my bike (a recently purchased 78 special): carburetors cleaned, cam chain tension, valve clearances, timing, ... the usual.

Slap on the carburetors and fire her up. She runs beautifully on the first kick [PO said it has been sitting for over a year]. I've been very excited about this. I took her around the block a few times, and before shutting her down, I give her a few revs. Seems like I have the infamous "sticking advance" problem.

The engine revs just fine up to about 3000, after which it gets stuck at just below 3k rpms. I suspected the advance unit, and sure enough, the weights get stuck at the advance position and don't return.

I wanted to know if I'm heading in the right direction with a solution:

Remove the weights and springs and advance unit.

Remove the pins in the advance rod and remove the rod itself.

Regrease the bearings.


This should solve the problem, right?

I was just wondering if the sticking is because of the advance rod or because of some errors with the weights.

The weights do not quickly return to the "resting" position-- they tend to get stuck on the way to being closed.


Also-- are there any particular or specific tools I will need for this that are not apparently mentioned? I seem to always find out there are random and very specific tools that I am missing that are required but not mentioned on a lot of tutorials.

I would really appreciate it if someone could let me know so I don't have to make multiple trips to the parts store.

If things go well, I think I might do a picture tutorial for points timing adjustment and this advance unit maintenance. I couldn't find a properly good one on any forum.

Thanks,

VCP

 

[5twins]

This will explain the advance rod and ATU servicing, no pics but pretty well explained .....

http://xs650temp.proboards.com/index.cgi?board=EngineStock&action=display&thread=1372

This is a fix for the advance if it is worn and advancing too much .....

http://www.xs650.com/forum/showthread.php?t=8636

No special tools are required and the only real "gotcha" is insuring the locating pins on the rod ends align or your timing will be 180° off. If lubing everything doesn't get the weights moving back in properly, you may need new springs. Actually, a fix for that is just to shorten one of yours. Clip one loop off (the hook) and bend out the next loop to form a new hook. Only do one at 1st, it's usually enough.

 

[VCPatel]

Thank you very much 5Twins. I appreciate your prompt reply. Hoping this goes without a hitch so I can get her out on the road.

 

[VCPatel]

Mr. 5twin-

Which parts in particular need to be regressed on the advance rod and the assembly?

I see that after removing the advance assembly there are bearings that are visible, but there isn't any mention of exactly where to apply grease so as to avoid the sticking problem. Should I just lightly grease the entire rod? Which bushings need to be greased and where are they located?

I apologize: new to the bike and anxious to get it unnig again. Also trying not to mess anything up.

Appreciate your help.

Vcp

 

[5twins]

There are 2 little bushings pressed into each end of the cam. The inner one is just a plain smooth bushing. The outer one, however, has grooves cut into it's I.D. These are there to be filled with and retain grease to keep the rod lubed for many years. Dip a Q-tip in solvent and clean the old grease out of the grooves (if there's any left, lol). Fill the clean grooves with fresh grease. Yamaha recommends a grease with moly in it. I use VW CV joint grease. It has a very high moly content. Smear the whole length of the rod with grease as well. It only rubs on the ends but it's only plain steel so can rust if moisture happened to get in there. The grease along the entire rod length is more for corrosion protection than lubrication.

Lightly grease the pivot posts for the advance weights before installing them. There is a very thin spring washer that goes under each weight. Try not to lose those. They stick to the backs of the weights sometimes when you remove them so check there for them if you don't see them on the posts. In the future, you can lube the posts with the ATU assembled by dribbling a little foaming chain lube on them. I like to do this on a warm engine so it penetrates better. Coat the springs too so they don't rust.

 

[js4016pk]

hey guys I know this is a really old thread but just have a quick question. I have a 75 and while setting my timing im noticing there is some slop or play in my advance rod unit..is this normal?

 

[VCPatel]

At the resting position I remember there being a tiny little bit of play; I believe that's normal. Want to make sure that the weights spring back to resting position after you pull on them (thereby loading the springs.)