Advance unit – normal or not?

[Tiggertoo]

Finally sorted the misfire on decel but a new problem has risen when doing dynamic timing. The timing advance goes well past the advance mark. I’ve read through dozens of threads on the subject but haven’t found what I think may be the problem.
Doesn’t seem to be much wear in the bob weights and I’ve tried replacing the springs, I’ve peened the bob weight ends so they are a good fit in the slots (they were pretty good to start with tbh). One thing that seems different from the pictures I’ve seen when searching the forum for ideas is that the gap between the weights and the housing stops seem to look a little larger on mine. Tried measuring them with a vernier caliper, one seemed to be 3.37mm and the other 3.32.
The stops appear to be bent outwards at a slight angle, do the pic’s look normal?
They don’t appear to have any obvious marks on them where a PO might have forced them apart, though I can’t think of any reason why someone should even try bending them open!
If they are bent I guess its time to get the wallet out and buy a new unit.

 

[Jim]

How much at full advance?
Here's how a lot of us here deal with it.. Adjust your timing so that at full advance, it's at about 38° or so.... and don't worry about idle advance. Yes, it's gonna be retarded at idle, but that won't hurt anything. Especially considering you spend very little time at idle in the grand scheme of things. One bonus to that is you'll find the electric starter will spin a little faster... easier starting with retarded idle timing.

 

[Tiggertoo]

Both cylinders are already retarded by a fair bit, firing directly above the F mark. If I retard much further it starts spluttering. Dwell meter says gaps are 22.5, When revved to 3,000 the timing mark goes way past the advance mark.

 

[Tiggertoo]

A couple more pictures, timing is set above F mark if it goes much further towards T it splutters at idle (1200rpm). At 3,000+ rpm the advance goes to about where the second picture shows.

 

[Jim]

Idle timing is anywhere between the yellow lines. On my run stand that uses points, I've set idle fire at the red line. Yes, it will start sputtering, you just need to bump the idle back up to 1200rmp or so and it'll smooth out. In some (very few) cases you'll also need to go back and readjust the idle mix screws.... but this is a tried and true method of working around too much advance.

Your alternatives are either buy another advance plate where the stops aren't bent, or gluing shims to the inside of the stops to restrict the bobweights.

 

[Jim]

OK... pics always help. That's a ton of advance. Looks to me like you'll need to buy a new plate to fix that much advance. I'd still glue some shims on the one on there right now just to run it and verify that's all that's wrong.

Btw, the metal used in the plate is too brittle to try and bend straight. It's been tried. Usually all you get for your troubles is cracks.

 

[Jim]

Oh, and my bad, I missed your first pic with the arrows pointing to the stops. Had I seen that I'd have gone straight to replace the advance plate.... sorry.

 

[Its been a long time]

If a new advance unit is on the cards, I'd have a go at bending the advance stop tabs in a bit. That's what the factory manual recommends, though I understand from posts here there's been cases of the metal cracking at the bend. Seems here, nothing to lose by trying though?

 

[gggGary]

Recently glued shims to the inside of the TX650 bob stops, a piece of pop can glued on w thick body super glue retarded full advance about 4 degrees. Next time I'm cutting my shims from a bean can. ;^)

 

[Jim]

Recently glued shims to the inside of the TX650 bob stops, a piece of pop can glued on w thick body super glue retarded full advance about 4 degrees. Next time I'm cutting my shims from a bean can. ;^)

https://www.onlinemetals.com/en/buy...clid=ADL-7100c9b2-f38b-4b79-a5e0-470b5ab85914

 

[Jan_P]

I dont have the plate here .So I can not check it
I would check it and consider to bend it back
In a vice or so
One can touch it with a file check if it is hard or hardened .I would not believe so
I believe it has been pressed ( dont know the English word ) in a tool

Mild steel can take a couple of bendings
If a Acetylene torch or other is in the shop it of course is an option to consider
Or take it to a place where such can be found hitting with a hammer when heated

Bending it cold can crack it .. worst case But if mild steel it would surprise me
I dont have the plate here .So I can not check it

Should it crack it possibly can be weld repaired

 

[Jim]

I dont have the plate here .So I can not check it
I would check it and consider to bend it back
In a vice or so
One can touch it with a file check if it is hard or hardened .I would not believe so
I believe it has been pressed ( dont know the English word ) in a tool

Mild steel can take a couple of bendings
If a Acetylene torch or other is in the shop it of course is an option to consider
Or take it to a place where such can be found hitting with a hammer when heated

Bending it cold can crack it .. worst case But if mild steel it would surprise me
I dont have the plate here .So I can not check it

Should it crack it possibly can be weld repaired

Because of the centrifugal force from spinning and the weight of the ... weights, it's hardened. Doesn't bend easily... cracks easily.

 

[Tiggertoo]

Well, I've bit the bullet and ordered a new unit: https://yambits.co.uk/xs650-auto-advance-governor-unit-points-models-only-p-23821.html
With a new one on the way I suppose tomorrow night I can start experimenting with shims, don't fancy trying to bend it and having it crack/break off while the engine is running. I'll have to research the right heat resistant glue first though

 

[gggGary]

There's a Yamaha service bulletin expressly saying don't bend those tabs, they'll crack. The early service manuals had it as a way to adjust the range, then they started seeing them break.

 

[Tiggertoo]

Shame on Yamaha for not incorporating some method of adjusting them. Maybe drilling/tapping the stops and have an adjuster screw? Anyone tried?

 

[gggGary]

Some info on this situation: https://www.xs650.com/threads/no-po...ouble-xs2-1972-xs650.50599/page-4#post-526280

 

[nightdancer]

Worth checking if the advance is hanging up or jamming.

 

[Tiggertoo]

Just to say thank you to everyone and to let you know that the new ATU (and other bits) turned up really quickly (for a change) and I fitted it last night. Interestingly after fitting the new ATU the timing was off, way too advanced and the dwell on the left cyl had dropped to 20 deg (RH cyl was still 22.5). My timing is now adjusted and advance is now back to normal just reaching the advance mark at 3,000rpm. I'm gonna keep an eye on those new points from Yambits as I've read on here that some aftermarket points are not great quality. I might see if there are some better quality ones out there as they don't cost much, just for my peace of mind.
I didn't get time to try shimming the old ATU as the new bits turned up so fast, but I will do so and keep it for spare in case the new unit causes any issues. Interestingly the stops on the new ATU are 90 deg to the back plate whereas the old ones are definately "splayed" outwards at an angle. The new ATU parts don't look to be interchangeable, weights are different shape, springs are smaller and the mounting post E clips are smaller than the originals.
I like to give closure on my threads just so folks know what worked and what didn't, its a PITA when you read so many threads where the OP hasn't let people know! Cheers folks

 

[Its been a long time]

Just to say thank you to everyone and to let you know that the new ATU (and other bits) turned up really quickly (for a change) and I fitted it last night. Interestingly after fitting the new ATU the timing was off, way too advanced and the dwell on the left cyl had dropped to 20 deg (RH cyl was still 22.5). My timing is now adjusted and advance is now back to normal just reaching the advance mark at 3,000rpm. I'm gonna keep an eye on those new points from Yambits as I've read on here that some aftermarket points are not great quality. I might see if there are some better quality ones out there as they don't cost much, just for my peace of mind.
I didn't get time to try shimming the old ATU as the new bits turned up so fast, but I will do so and keep it for spare in case the new unit causes any issues. Interestingly the stops on the new ATU are 90 deg to the back plate whereas the old ones are definately "splayed" outwards at an angle. The new ATU parts don't look to be interchangeable, weights are different shape, springs are smaller and the mounting post E clips are smaller than the originals.
I like to give closure on my threads just so folks know what worked and what didn't, its a PITA when you read so many threads where the OP hasn't let people know! Cheers folks

Good to hear. I have been on the lookout for Daiichi points and bought a set but they turned out to be for XS1/XS2 and wouldn't fit my 77 650. I gave up with points after having Chinese condenser and points which were bad out of the box. I didn't buy from Yambits, in the picture on their website they're clearly Chinese and I don't trust them. Yamaha points and condensers are available but by the time I paid shipping, tax etc (they were in Japan) they were maybe 2/3 the cost of an electronic ignition conversion. Anyhow, good luck with it. I have new E clips that will fit the old advance unit. I can post a couple out if you like.

 

[WideAWAKE]

Genuine NOS for points and condensers.

Don’t fit or DOA too many times with anything else. A shame but true.