Cannot stop throttle shaft seal leaks

Hi Robert, no resolution on my side to the seal leaks just yet. Sorry I can't be of much help at this point. However, I picked up a timing light this week and learned some important things tonight that may be worth considering as you trouble shoot... I think some of my issues may be related to basic engine timing. With the suggestions of previous posts in this thread to consider the timing advance unit hanging up, I've been thinking about the odd performance variations as timing advance related and not carb mix as I ride and make mental notes.

I checked this week and am pretty sure the advance unit weights not hanging up. Everything seems lubed and strong. However, I notice there is some play in the weights and remember people talking about re-fabricating the ears with JB-weld to build them up and remove the play in some threads. How much play is too much? I need to take a moment and look more closely at the weights again with a timing light. I've attached a video of the slop in the weights to ask opinions:


Now the main event for this post... I've been setting my points gap with a feeler gauge at 0.016" and using my multimeter as a buzz box to set when each point is making contact while rotating the timing plates. Sometimes I have to fight and shift/regap the individual points to get the blocks in the proper location on the cam for the fire marking. The latest points set that I bought came as a set with a condenser on eBay. The quality is a little less than I like (certainly lower quality than the originals on the bike). I've only set static timing previously, as I did not have access to a timing light. Even after setting and getting the meter to match properly, I occasionally have to make a very subtle adjustments on the main plate because timing needs adjusted further... Finally now experimenting with a timing light tonight, and each sparkplug was firing way off! The left cylinder was firing just a hair before TDC and the right cylinder was firing almost 10 degrees after TCD! I can't believe I've been running it like this. I'm pretty sure the multimeter seemed fine when I rechecked them with static method tonight? I still don't know how to explain the shaft seals in the carbs leaking, but this timing discrepancy potentially explains so many other patterns on my bike.

I've now dynamically set the engine timing using the timing light and took it for a test run after. Such a significant difference! It had an immediate power that I've not seen. I also was able to re-adjust the idle screw and set the mixing screw on the carbs down to the 2.25 turn spec. For the real test, we'll have to see how it cold starts in the morning.

A concern that I have with this current timing is that I have turned both timing plates both as far clockwise as they can go, but I still don't think they are firing close enough to the F mark on the stator cover. Is this a matter of a worn cam between the points or are the points possibly deformed? Anything else? I suppose I need to get a degree wheel and mark more accurately on my PMA, but in the mean time I've attached a photo of where I currently have each cylinder set to fire while running with a timing light . Any thoughts? Is there are way I can push it to fire earlier or am I in about the right spot?

Thanks also, 2Many for the link suggestion regarding spigot leak. I think Mailman may have similarly shared the part of it with his choke casting issues previously. After a general skim beyond page 10, that mammoth thread pretty much seems to address anything that can possibly need serviced. I've officially bookmarked it now...

Still always so much more to learn...
 

Attachments

  • IMG_2435.png
    IMG_2435.png
    1.9 MB · Views: 213
  • IMG_2434.JPG
    IMG_2434.JPG
    326.7 KB · Views: 203
authenticnovelty said:
Hi Robert, no resolution on my side to the seal leaks just yet. Sorry I can't be of much help at this point. However, I picked up a timing light this week and learned some important things tonight that may be worth considering as you trouble shoot... I think some of my issues may be related to basic engine timing. With the suggestions of previous posts in this thread to consider the timing advance unit hanging up, I've been thinking about the odd performance variations as timing advance related and not carb mix as I ride and make mental notes.

I checked this week and am pretty sure the advance unit weights not hanging up. Everything seems lubed and strong. However, I notice there is some play in the weights and remember people talking about re-fabricating the ears with JB-weld to build them up and remove the play in some threads. How much play is too much? I need to take a moment and look more closely at the weights again with a timing light. I've attached a video of the slop in the weights to ask opinions:


Now the main event for this post... I've been setting my points gap with a feeler gauge at 0.016" and using my multimeter as a buzz box to set when each point is making contact while rotating the timing plates. Sometimes I have to fight and shift/regap the individual points to get the blocks in the proper location on the cam for the fire marking. The latest points set that I bought came as a set with a condenser on eBay. The quality is a little less than I like (certainly lower quality than the originals on the bike). I've only set static timing previously, as I did not have access to a timing light. Even after setting and getting the meter to match properly, I occasionally have to make a very subtle adjustments on the main plate because timing needs adjusted further... Finally now experimenting with a timing light tonight, and each sparkplug was firing way off! The left cylinder was firing just a hair before TDC and the right cylinder was firing almost 10 degrees after TCD! I can't believe I've been running it like this. I'm pretty sure the multimeter seemed fine when I rechecked them with static method tonight? I still don't know how to explain the shaft seals in the carbs leaking, but this timing discrepancy potentially explains so many other patterns on my bike.

I've now dynamically set the engine timing using the timing light and took it for a test run after. Such a significant difference! It had an immediate power that I've not seen. I also was able to re-adjust the idle screw and set the mixing screw on the carbs down to the 2.25 turn spec. For the real test, we'll have to see how it cold starts in the morning.

A concern that I have with this current timing is that I have turned both timing plates both as far clockwise as they can go, but I still don't think they are firing close enough to the F mark on the stator cover. Is this a matter of a worn cam between the points or are the points possibly deformed? Anything else? I suppose I need to get a degree wheel and mark more accurately on my PMA, but in the mean time I've attached a photo of where I currently have each cylinder set to fire while running with a timing light . Any thoughts? Is there are way I can push it to fire earlier or am I in about the right spot?

Thanks also, 2Many for the link suggestion regarding spigot leak. I think Mailman may have similarly shared the part of it with his choke casting issues previously. After a general skim beyond page 10, that mammoth thread pretty much seems to address anything that can possibly need serviced. I've officially bookmarked it now...

Still always so much more to learn...
Click to expand...

Yea a timing light is an essential tool. I'm pretty sure my advance unit is ok but I will try gary's test tomorrow to confirm. I read in this post that someone covered the throttle shaft seals with dielectric grease?? Never heard of doing that. Would probably just stop the leaking for a little but not completely. If you don't mind me asking how do you sync your carbs? I use a drilled out grease nipple screwed into the carb and hook up my manometer to it, seems to work ok but the meter is very sensitive and it fluctuates often; also not sure if I should even be syncing the carbs if I have leaks on both carb seals.
 
Yeah, there's a bit of slop in those advance weight ears. More than I like, but it'll run.

When the engine is running, the drag of the points followers will pull the advance unit to its full retard position. That doesn't necessarily happen while doing static timing, hence the reason to follow up with a timing light.

Long ago, I mig-welded a little build-up on those ears. Then, ground them down, maintaining the curved profile, to a much closer 0.002" fit into the slots. This weld/grind repair fixed my severe spark scatter. Don't use JBweld.

Having your points plate rotated fully Clockwise indicates a combination of worn advance weight ears and a stretched camchain.

For your timing marks, have you seen this?

http://www.xs650.com/threads/pma-timing-tab-got-the-simple-solution-for-you.13345/
 
Robert, I’m using dead cylinder method to sync at the moment has been sufficient, but as i get closer to figuring out problems with my biks vs. what user error i’m guilty of, I’m probably going to buy the motion pro permanent carb ports next time i put an order in on mikes or dime city and build a manometer.

This is where i originally heard about applying dielectric grease to seals:

How are you installing your seals?

2many, thanks for these suggestions. Making a mental note for my symptom list regarding timing plate. All very helpful. Are there suggestions for fixing the ears on weights aside from buying new from mike’s? Thanks also for the timing mark thread. I’ve seen the stickers and need to do something about that.
 
If your motor is whirring you need to address that "first".
I suspect many XS650's have had the cam chain "tightened", destroying the chain and front guide.
Then; I've gotten points ignitions hammered into working "well" but why? Probably the BEST thing you can do to a points ignition XS650 is toss all that old crap and buy an integrated genuine from yamahaxs650.com pamco/e-advance, install, set, run.
We wax romantic about our old rides but some parts are better remembered than used.
 
Last edited:
spot on electronic ignition timing and advance every time all the time ....instant starting and perfect running .. no maintenance and no more fiddling around with mechanical points and advance .
what is not to like ?:)

Its a no brainer and imho the best upgrade you can buy for a xs650
 
Yes, you need to re-do your timing marks. You also appear to be missing one, for full advance. That mark is very important and you have to check the timing at full advance to make sure it's not over-advancing. Over-advancing can hole a piston and has done so on many of these bikes. It's probably a blessing in disguise that you can't get the timing dialed in exactly on the "F" mark. You are set slightly retarded which means you most likely are not going past the full advance mark. This is a good thing. Many of us feel these bikes actually run better with the timing set like this, a few degrees retarded.

The advance unit is made to advance the timing a certain set amount, 25° when new. As it wears and the parts loosen up, the amount it advances grows. That means that eventually, with the idle timing set on the "F" mark, the advance timing will be past it's mark and too advanced. This is why you must check your timing at both idle and full advance. Personally, I don't think your advance looks too badly worn. Mine has more "slop" in it than that and still works fine. But, the only way to accurately check the extent of wear on your advance is to check your timing at full advance.

If you do want to try and get the timing mark closer to the "F" mark, reduce your points gaps a little. Set them at .014" instead of .016".
 
peanut said:
spot on electronic ignition timing and advance every time all the time ....instant starting and perfect running .. no maintenance and no more fiddling around with mechanical points and advance .
what is not to like ?:)

Its a no brainer and imho the best upgrade you can buy for a xs650
Click to expand...
Yea but that kit is more money than I paid for the bike originally! Not going to say how much I put into getting it running!
 
gggGary said:
The purchase price of any old bike is merely buying a permit to spend SERIOUS cash in a quest to have reliable transportation.
Click to expand...
I fully understand that rule! I was just making a joke. Besides I spent over $200.00 at Mikes for wiring harness along with odds and ends back in 2008 and took about 10 years to even start working on the bike that I only paid $75.00 for to begin with!
 
gggGary said:
timing should advance smoothly from fire to the Advanced mark at about 3000 rpm. Throttle up and down from idle to 3000 several times, you are watching for consistent smooth movement to the full advance mark and back to F
Click to expand...

Ok so I just did the timing test. The mark on my rotor doesnt really stay in one position consistently, it sort of jumps back and forth a few milimeters wherever it is. When I held the idle at 3000 rpm the mark stayed in the middle and dident go past the full advanced mark. When I throttled up to 3000 the mark was kind of spastic. I would not call it "smooth".
 
I'll try to be clear;
A bit of "jumping about" is part of points ignition, old worn points more so. What we are looking at is the advance mechanism; so from idle, rev it smoothly to 3000 RPM, let it return to idle watch that the timing advances to full (ish) advance then goes back to the F mark as RPM goes back to idle. A problem with the advance would be if the engine goes to idle but the timing stays "stuck" at full advance "for a while" or never goes back all the way to the F mark. While you have the light, check timing on BOTH cylinders they should match closely, at both idle and full advance.
 
gggGary said:
I'll try to be clear;
A bit of "jumping about" is part of points ignition, old worn points more so. What we are looking at is the advance mechanism; so from idle, rev it smoothly to 3000 RPM, let it return to idle watch that the timing advances to full (ish) advance then goes back to the F mark as RPM goes back to idle. A problem with the advance would be if the engine goes to idle but the timing stays "stuck" at full advance "for a while" or never goes back all the way to the F mark. While you have the light, check timing on BOTH cylinders they should match closely, at both idle and full advance.
Click to expand...

Ok I gotcha. I have a pamco ignition for 277 rephase by the way. I revved the bike to 3000 rpm and the mark goes back to the F mark. It doesnt hang around full advanced when going back to idle.
 
My bad I didn't read your siggy. Kinda have a 2 OP thread going here, good to know the advance is working well. Since the pamco is on the cam you will see some timing movement from cam chain slack and harmonics. There is no way to avoid that with a cam based ignition trigger. pamco or points.
 
Never hurts to do a TDC check with a piston stop, confirm the rotor and "T" mark line up when at true TDC. All things considered betterto be a bit retarded than advanced. A sure sign of excessive idle advance is kick back or a "stop" when kick or electric starting. My thumb nail time iwth no equipment handy is advance iggy til it kicks, then back off till that stops. That'll be pretty close to right.
 

Similar threads

Fingerscrossed
Flames from carb on throttle
Replies
12
Views
570
Fingerscrossed
Fingerscrossed
Notmyrealname
Shaft Seal Part Numbers
Replies
10
Views
172
Notmyrealname
Notmyrealname
fenbrancis
Direction of Throttle Shaft Seal
Replies
10
Views
813
GLJ
GLJ
I
Not another VM34 post
Replies
19
Views
415
Kevin Werner
Kevin Werner
H
Proper Jetting and Fuel/Air Screw Position Mikuni VM-34 on a 1972 Yamaha XS2 (650)
2
Replies
31
Views
955
Hanniusms
H
Back
Top