Loss of power, PAMCO

[vincejames]

Recently, I've been experiencing some difficulties. In 3rd and 4th gear, all of a sudden I loose power and when I hit the throttle I go nowhere. The bike still runs, but it sort of bogs down. I'm not sure if it runs on one cylinder or what. One time while this happened I even blew my main 15 amp fuse.

I traced the blown fuse back to my ignition/key switch and replaced. The old key switch was from Lowbrow, which I will never buy again; considering it's only about 2 years old. I replaced with a Honda OEM ignition switch. This cured the blown fuse problem, but I'm still having issues with the bogging down in 3rd and 4th gear. It's not a continuous problem, it more comes and goes.

My first thought was that I might have an air leak or gas isn't getting to my carburetor fast enough. My petcocks are vacuum type and I replaced both of them about a month ago. There is no air leak when I spray carb cleaner around the seals of the manifold.

A mechanic buddy of mine said that I might need to upgrade my points ignition to PAMCO. He said this might help. I'm running a Hugh's Handbuild PMA system. Opinions?

1978 Yamaha XS650 BS38s. Straight pipe exhaust, no baffle, 145 main jet, 45 pilot jet, fuel/mixture 2.25 turns out.

 

[5twins]

Has your advance rod been serviced and well greased? It could be sticking at times and not allowing the ignition to advance properly. That could cause bogging.

Are you sure about that 45 pilot jet size? That's awfully big for a '78-'79 carb set. Stock was a 27.5 VM22/210 type. For mods, a 30 or 32.5 is the usual choice.

 

[vincejames]

Hey 5twins. Thanks for the timely response. I'll take a look at both and see what I can find.

Thanks.
Vince

 

[vincejames]

Opinions on what to use grease wise?

Thanks,

 

[5twins]

The factory recommends a grease with moly in it. I use VW CV joint grease as it has a very high moly content. The fact that you say you're going to check the rod tells me you never have, lol. Keeping it lubed is a required maintenance item but not many know it. It was never mentioned as such in any of the manuals. I consider it a "must do" on any "new-to-you" 650 because chances are, it hasn't been serviced since it left the factory.

 

[vincejames]

No I have not yet. Thanks for the help! I'll take a look today and post some photos to this thread on my findings!

 

[5twins]

Here's a thread to help with the servicing .....

http://www.xs650.com/threads/rpms-hover-but-not-finding-air-leak.18187/

 

[vincejames]

I'm 100% going to try this out but, isn't this usually a remedy for high hanging idles?

 

[5twins]

Yes, many times it is, but that is to correct the rod sticking in the advanced position. You may have the opposite happening, the rod may be sticking in the retarded position, not allowing the ignition to advance as the RPMs increase. Properly greasing it should cure either problem.

Here's what I think could be happening - as you run up through the gears, you close the throttle to shift. The RPMs fall and the ignition & advance rod return to the retarded setting. You roll the throttle open after shifting and the RPMs try to increase. The ignition and advance rod try to advance but if the rod is stuck, that won't happen. The motor bogs down. It won't run right at higher RPMs if the timing is retarded.

 

[vincejames]

This actually seems like it is the EXACT problem. When then engine bogs, the only way it stops is when I shift through the gears and open and close the throttle, eventually the bike comes back to normal and it rides perfect again.

Thanks - Vince

 

[5twins]

Like I said, this should be considered a routine maintenance item. It doesn't need to be done often, maybe every 5 years or so, but it has to be done occasionally. As I also mentioned, most haven't had the advance rod greased since it was assembled at the factory over 30 years ago. They're long overdue.

 

[vincejames]

So I wanted to bring this thread full circle, mainly for 5twins, Below are some images of what I saw when I took the points cover off and the advance cover off. It definitely looked like I needed some CV Joint Grease. I followed 5twins instructions, and believe that I did this all correct. I also changed my pilot jet from a 45 to a 30. After a test drive my bike ended up running terrible, so I'm thinking I did something wrong. It was noticeably louder and had a very loud metal ticking coming from the top end. At idol, the RPMs were jumping around from 800 to 1500. I pretty sure I assembled everything correctly. Some more help would be greatly appreciated. Below is a little before and after from doing the advance rod servicing - videos

Before:

After:

 

[5twins]

Well, your advance unit and rod definitely needed servicing and it appears you have them working correctly again. I notice you removed the points plate during the process. Did you accurately check/set timing again after putting things back together? If you just marked the plate and put it back where it was, the timing could be off. Remember, it was originally set with a faulty sticking advance. The advance may not have been in the full retard position when you set the timing. The top end ticking I'm not sure about but it could be related to the timing if it's off. How easy does the bike start? It won't start easy if the timing is too far off.

As far as the pilot jets go, did you use the proper VM22/210 style pilot jet required for a '78 carb set? You are using '78 carbs, right?

 

[vincejames]

Yes, the advance unit was getting stuck open. I lubed the rod and placed it back in making sure all of the marks you had illustrated lined up correctly. As for the points plate, I removed the plate by unscrewing the two screws. I took a photo then put the plate back on exactly the way I took it off. When I started the bike after greasing the advance rod, it had trouble starting. I then replaced the pilot jets and it started a lot easier. The pilot jets were purchased from mikes a couple months ago. They are brand new.

Can you point me in the direction of a good thread to help me check.set the timing? I think this might be the issue.

 

[5twins]

This thread explains the timing and setting. You should use a timing light, it's the most accurate method .....

http://xs650temp.proboards.com/thread/7984

You didn't answer the question about your carbs. Are they '78 carbs? And the pilot jets you installed may be new but are they the correct VM22/210 type? The 650 carb sets used two different styles of pilot jets over the years. They look the same from the outside but are set up differently internally. They flow differently. You have to use the type your carb set was designed for.

 

[vincejames]

I believe they are 78 carbs.

 

[vincejames]

best photos I have at the moment

 

[5twins]

Yes, that is a '78 (or '79) carb set.

 

[scott s]

From 45 to 30 is a huge change on the pilot jet. AND, you say in your original post that you're having trouble in 3rd and 4th gear. You should be well off the pilot jet by then.
You should be looking at the needle clip position and/or main jet size, if....IF...in fact this is a jetting issue.

When's the last time you did a valve adjustment or put a timing light on it?

 

[vincejames]

My valves check out according to chlymer. Timing was done recently. I'm going to go through everything again soon. Timing, valves, carb cleaning.

I've never replaced the needles. Only float seats, main jet, pilot jet.

If I can't figure this out by end of weekend, I might have to look to new carbs and PAMCO. As much as I feel that BS38s shouldnt need to be replaced and that a good cleaning, rebuild should do the trick, it might become my only option. Also, I sure as hell don't want to admit a failure and just replace points with PAMCO, but it might be the only option too...grrrr!