Need help with engine knocking/electrical problems

[pjm204]

Well first I will start by saying hello, i've been reading here for awhile but just decided to join. I'm a regular over at GStwins.com but that is pretty much just a gs500 site. Considering I have some older GS's now, I figure the right answers will be found here.

I recently picked up a second gs400, a 1977. The bike was in somewhat rough shape when I got it. Missing lots of nuts and bolts, the front brake caliper was frozen together and hanging from the bars. It had no paint on the tank or tail, no battery, fuel lines disconnected, and other random things wrong with it.

Since then, I have done the following to it:
1. Adjust valves
2. change oil
3. paint tank/tail
4. bleed front brake/attach
5. switch bars
6. replace lots of screws
7. fix some wiring


Here is what still needs to be done:
1. recover seat
2. get horn to work
3. Brake lights only go on when pressed HARD
4. find an air filter
5. find a right sidecover
6. Gear indicator identifies wrong gear, says 4,8,9...neutral does not light up.
7. Fix engine knocking


The engine knocks while idling until it is warmed up. It is coming from the top of the engine and is pretty loud. I am not sure what it could be. Once the bike warms up awhile, it seems to go away. The bike does seem to vibrate a bit more than my other gs400 when idling. Anyway, if anyone has any advice for this or any of the other things I still need to finish, please let me know. Thanks, here are a few pics of before, and now

 

[tkent02]

Nice work so far, it looks great!
Are you sure you got the valves set correctly?

Knocking could be...
Piston slap?
not likely on these GSes.

Connecting rod bearing getting too loose?
probably wouldn't go away with the engine being warmed up, and you should hear it more at higher RPM, not at idle.

Could a shim have broken or come loose or something?

Do the twins ever get clutch rattles like the 1000s?
Dunno, haven't had twins for a long time.

 

[bwringer]

As to the noise, I would suspect a good carb sync would take care of it. If that's already been done, then perhaps there's an intermittent spark problem on one side.

 

[pjm204]

I took it for another short ride....knocking did not go away after it was warmed up. It had very little power, I had trouble getting it over 5500rpms. also wasn't smooth, it would continuously change speeds, i mean only slightly but it was as if I was pulling in the clutch every so slightly every couple seconds. Lastly, the petcock seems to be leaking a bit, but it looks like it is leaking out the gasket between the tank and petcock, any advice here?

I adjusted the valves a week ago but it was my first valve job ever so I may have put the wrong shim size in on one of the four valves, that's possible.

Left spark plug was dark but the right one looked perfect......????

oh last thing, after I shut off the bike, the battery still makes some noise, sounds like when it is being charged...does this mean it is being drained when the bike is off?

 

[tkent02]

Sounds like you need to get a service manual, go through it step by step, go through the Stator Papers here, and find out what all the different problems are. I think there's quite a few. Make it run as well as it looks.

 

[Nessism]

Did the engine make the noise before your valve adjustment? How far out of adjustment were the valves?

 

[pjm204]

I've got the service manual.......yes the engine made the noise before I did the valves. They were pretty tight.

 

[rustybronco]

If you pull in the clutch at idle does the noise go away?

 

[TheCafeKid]

Does it go away OFF idle, (with throttle)? If so, it may be a lil cam chain slap

 

[pjm204]

The knocking does not go away with the clutch pulled in. It does seem to go away when the bike is revved, but I just may not be able to hear it.....

as for the loss in power? my first thought would be loose valve clearances? What else could it be?

 

[Killer2600]

I adjusted the valves a week ago but it was my first valve job ever so I may have put the wrong shim size in on one of the four valves, that's possible.

Lucky! I have to adjust my valves soon and I have to do all 16 of them

 

[Suzuki_Don]

Lucky! I have to adjust my valves soon and I have to do all 16 of them

Yes, but you dont have shims.

 

[Guest]

Lucky! I have to adjust my valves soon and I have to do all 16 of them

Believe me. We are the lucky ones. Shims suck.

 

[TheCafeKid]

Believe me. We are the lucky ones. Shims suck.

Bahhh.. Bill you just have to get into the ZEN of shims. And Killer there will be lucky, untill his 16v 750 motor spits its oil gears out, then he will be cussing I must say, having played with the adjustments on the CBs i had, which were tappet adjusters like the 16v GS, and started on the lil KZ i have now, which are the same, it IS easier. MUCH. But, I still like the reliability of the shim over bucket so far. Granted these are the first two bikes ive owned that ARE shim over. I have had shim under as well, and THAT is a PITA big time from what i collected (i didnt do them, my dad did) But, having learned how to do the GSs shim over, now i can do my Volvo too...it uses the same design, only single cam. LOL

 

[pjm204]

So because I have a weird loss of power and the bike is almost incapable of going over 5500rpms, would that be a sure sign that the valves are too loose? I really want to figure out what is wrong with the bike, I'm fixing it for someone so the sooner the better.

 

[Nessism]

Loose valves won't cause the problem you describe. Something else is wrong. You might want to check the compression to see if there is anything noticeably wrong.

 

[pjm204]

well I re-did the valves, they were way off. That helped with the loss of power and it no longer burns any oil, but there is still a noise.
I am not sure I'd call it a knock. It happens every few seconds during idle, may happen while riding but I can't hear it. It could be cam chain slap...not sure. any advice?

 

[pjm204]

I rode the bike and had a mechanic listen to it. Of course when I get there the bike isn't making a sound. He said his best guess is that the bike is only firing on one cylinder at start up and then once it is warm the second cylinder kicks in and it stops knocking.....

it seems to only do it when it is below around 1700 rpms. It seems to blow some smoke out the left pipe until it warms up. Could this be an electrical problem?

 

[Suzuki mad]

Well first I will start by saying hello, i've been reading here for awhile but just decided to join. I'm a regular over at GStwins.com but that is pretty much just a gs500 site. Considering I have some older GS's now, I figure the right answers will be found here.

I recently picked up a second gs400, a 1977. The bike was in somewhat rough shape when I got it. Missing lots of nuts and bolts, the front brake caliper was frozen together and hanging from the bars. It had no paint on the tank or tail, no battery, fuel lines disconnected, and other random things wrong with it.

Since then, I have done the following to it:
1. Adjust valves
2. change oil
3. paint tank/tail
4. bleed front brake/attach
5. switch bars
6. replace lots of screws
7. fix some wiring


Here is what still needs to be done:
1. recover seat
2. get horn to work
3. Brake lights only go on when pressed HARD
4. find an air filter
5. find a right sidecover
6. Gear indicator identifies wrong gear, says 4,8,9...neutral does not light up.
7. Fix engine knocking


The engine knocks while idling until it is warmed up. It is coming from the top of the engine and is pretty loud. I am not sure what it could be. Once the bike warms up awhile, it seems to go away. The bike does seem to vibrate a bit more than my other gs400 when idling. Anyway, if anyone has any advice for this or any of the other things I still need to finish, please let me know. Thanks, here are a few pics of before, and now

One area you haven't talked about or done. Fuel and carbs.

They probably could do with a strip and clean.

I suspect that its a blocked or clogged fuel filter inside the carb.

Suzuki mad.

 

[pjm204]

I've been thinking about the carbs as well. I think I may have a blocked pilot jet since it only happens at low RPMS. I took the ignition cover off and found that the points for the left cylinder were out of spec, gap was too wide. I'm currently trying to adjust the timing since one of the screws was real lose, I think the guy I bought it from was attempting to do work on the bike and stopped.

There was no filter in the bike at all so I bought some uni filter foam and put it in the airbox and then made a cover out of lexan for the airbox. I couldn't find a stock filter.

Also the air/fuel screws were waaaay too rich, plugs were really black, now they are started to clean up.

I really don't want to take the carbs off but I guess I have to, I hate messing with the airbox.