hole in the exhaust - 79 GS850GN

[wideload]

I have a 1979 GS850GN, which I manage to keep it running fine with help from reading all the past articles in this forum, so first off, I would like to give a BIG thanks =D> to Keith Krause, Lynn, Hoomgar, argonsagas and other who have help others in-turn helping me

While doing spring clean-up of my bike, I found that there is a hole on my left exhaust about the size of a quarter The rest of the exhaust is fine and the right side exhaust has no rust/hole (outside anyway).

Is it okay to just plug up the hole with muffler patch (I read j-b weld can't take the temp extreme) to save money? If so, will it last.

Or should I just replace it with a MAC 4-into-2 as suggested in other posts. And if I understood correctly, changing it to a MAC 4-into-2 exhaust with stock airbox doesn't require rejetting - which I'd like to avoid, I don't think I have the skills/patience for it.

Thanks in advance for your help.

Don

 

[Cajun Cycler]

It won't hurt to patch it. Just depends on whether or not you are worried about appearances as to replace the mufflers or not.

 

[wideload]

It won't hurt to patch it. Just depends on whether or not you are worried about appearances as to replace the mufflers or not.

The hole is at the bottom of the muffler so appearance wise it's ok. Have you tried it? How long does it last?

 

[bwringer]

I patched a pipe on my wife's bike several years ago, and it's still fine.

The kit had a small sheet of some thick white fibrous material plus a section of screening and a couple of clamps. The sheet of white stuff went over the hole, the screen went over the sheet, and I used hose clamps to hold the assemblage together.

I've also seen kits that would probably be better that use a small sheet of stainless steel. The screening used on my wife's bike starts to look rusty after a while, but it's still holding up.

 

[wideload]

I patched a pipe on my wife's bike several years ago, and it's still fine.

The kit had a small sheet of some thick white fibrous material plus a section of screening and a couple of clamps. The sheet of white stuff went over the hole, the screen went over the sheet, and I used hose clamps to hold the assemblage together.

I've also seen kits that would probably be better that use a small sheet of stainless steel. The screening used on my wife's bike starts to look rusty after a while, but it's still holding up.

I guess if done properly it will last. I plan to go down to my auto parts store to see what muffler patch kit they have. Hope they have the stainless steel one. Thanks for the response.

 

[KEITH KRAUSE]

As stated above, the patch should work if applied correctly.
As for a new pipe requiring a re-jet, if the bike is running well and you're happy with it, take some plug reads at 1/3 and full throttle. Note their color. Should be a tan or tan/gray insulator. Just be sure to apply the patch first.
If you still decide to get the new pipe (and new exhaust gaskets), do the plug tests again. Do what the plugs/performance tell you. Any changes will obviously be related to the pipe. The plugs will tell you if it needs a re-jet. Don't trust the makers claims. If the pipe flows significantly better, the plugs will show this and it WILL need a re-jet. If it doesn't flow much better, or at all, and the plugs look close to the same, no re-jet.
And thanks for the thank you.

 

[Can_O_Tuna]

FYI...I used J/B weld on my old Header (with stainless screen) and it held up to the heat, do the first layer with the screen and smooth the second layer on by itself.

The problem with todays muffler patch is that they have eliminated the asbestos.

 

[wideload]

As stated above, the patch should work if applied correctly.
As for a new pipe requiring a re-jet, if the bike is running well and you're happy with it, take some plug reads at 1/3 and full throttle. Note their color. Should be a tan or tan/gray insulator. Just be sure to apply the patch first.
If you still decide to get the new pipe (and new exhaust gaskets), do the plug tests again. Do what the plugs/performance tell you. Any changes will obviously be related to the pipe. The plugs will tell you if it needs a re-jet. Don't trust the makers claims. If the pipe flows significantly better, the plugs will show this and it WILL need a re-jet. If it doesn't flow much better, or at all, and the plugs look close to the same, no re-jet.
And thanks for the thank you.

Will do the chop test once I've patch it up. [-o< I Hope don't need to deal with re-jetting. Thanks again.

 

[wideload]

FYI...I used J/B weld on my old Header (with stainless screen) and it held up to the heat, do the first layer with the screen and smooth the second layer on by itself.

How long did you keep your old header?

The problem with todays muffler patch is that they have eliminated the asbestos.

Asbestos help with heat?? Or other advantages?

 

[wideload]

Bike runs great

Bike runs great

FYI...I used J/B weld on my old Header (with stainless screen) and it held up to the heat, do the first layer with the screen and smooth the second layer on by itself.

The problem with todays muffler patch is that they have eliminated the asbestos.

I went with Can_O-Tuna's advise and use J/B weld. Figure if it held up fine on a header it'll be ok on the muffler. So far so good. Thanks Can_O_Tuna for your response.

Here is what I did to my bike other than patch up the exhaust:

1. replace exhaust gaskets
2. clean up carb and replace o-rings (from Robert Barr)
3. replace Intake O-ring
4. Clean up Electrical connections, fuse box and added new ground
5. get new Maintenance free battery and tender
6. replace gear oil, motor oil, brake fluid, fork oil
7. got the Napoleon mirrors
8. valve clearance adjustment (diff shim sizes)

After that the bike started right away, just with one crank \\/ Warm it up. Check air screw adjustment, hook up the vacumm sync tool and the Carbs are in sync without any adjustments!!! :-D (within 2 HG, and even on all four at other rpm's) Thanks to Keith's Bench sync instructions.

I haven't had the chance to do a chop test yet but my GS runs better than I could remember.

Thank you all again for all your input, especially Keith. There is no way it could have gone this smooth without pouring through all the contents on this forum. Thank you Frank for your time and effort and keeping this forum up.

One question. Is it normal to get popping noises while warming up on choke as this will richen it up? Once it warms up the popping sound from exhaust disappears. BTW it takes a lot quicker to warm up now:-D it use to take forever

 

[KEITH KRAUSE]

Not sure what you mean by "popping" because it can vary some as to what's happening. We all describe noises in general a little differently.
Popping, like when the engine is idling and an irratic POP accompanies the idle, can be rich or lean related. Just because you're using the choke at that time doesn't mean it's rich (we all generally use choke to start a cold engine). It could actually be lean at this time and the choke can't richen the mix enough. Hard to say but more often than not, it is a rich condition.
Many things on your repair list could cause this if done incorrectly. I assume it didn't do it before the work? I forgot, what mod's do you have?
Any chance you're over-chooking it? Or are you just using the choke as always?
Side air screws positively set for highest rpm, using 1,000 rpm as a base for adjustment? Where are the pilot fuel screws set (underneath)?
Clean air filter? If points, points clean and flat, fresh/good condensors, dwell set, timing set?
Leaking exhaust gaskets will cause a pop, in this case a lean condition. It can be difficult to get a header to uniformly compress the gaskets well and you don't dare over-torque. I think 9-10 ft/lb is max on most models?
And of course, many things inside the carbs can cause a popping.
Thanks for letting us know we helped.

 

[wideload]

Not sure what you mean by "popping" because it can vary some as to what's happening. We all describe noises in general a little differently.

like a mild backfire. holding my hand on the back of the exhaust I can feel it pulsating. This was happening for as long as I can remember, but since the bike is running so much better:-D , I figure if this is not normal I might be able to fix it too. After about a minute warming up (or less, I didn't time it). It goes away and the bike just idles beautifully. Revs fine with no hesitation once warmed up.

Popping, like when the engine is idling and an irratic POP accompanies the idle, can be rich or lean related. Just because you're using the choke at that time doesn't mean it's rich (we all generally use choke to start a cold engine). It could actually be lean at this time and the choke can't richen the mix enough. Hard to say but more often than not, it is a rich condition.
Many things on your repair list could cause this if done incorrectly. I assume it didn't do it before the work? I forgot, what mod's do you have?
Any chance you're over-chooking it? Or are you just using the choke as always?
Side air screws positively set for highest rpm, using 1,000 rpm as a base for adjustment? Where are the pilot fuel screws set (underneath)?
Clean air filter? If points, points clean and flat, fresh/good condensors, dwell set, timing set?
Leaking exhaust gaskets will cause a pop, in this case a lean condition. It can be difficult to get a header to uniformly compress the gaskets well and you don't dare over-torque. I think 9-10 ft/lb is max on most models?
And of course, many things inside the carbs can cause a popping.
Thanks for letting us know we helped.

My GS is all Stock. I have clean the foam air filter and use foam filter specific oil. The points are fine, timing with a timing gun show perfect for advance but idling the line doesn't line up perfect but very close. Condensors was just replace last year, but I get blue spark on all four plugs. I have check the plug gaps as well.

When I check the air screw for highest rpm, I found the rpm goes down, so to get highest rpm I just put it back to the way it was, line-up with the mark which may have come from the factory.

i gently seat the pilot fuel screw and wrote down how many turns and took a picture to remember their position before removing and cleaning them. And as far as I can tell I return them back to original setting.

The exhaust gaskets are new, I believe it tight enough as I don't want to overtighten but I had someone else check it as well. will double check with torque wrench.

What do you think?

Thanks Keith

 

[wideload]

By the way the airbox cover rubber gasket expanded (damaged) so I had to use weather stripping and duct tap. Duct tape the top portion of both side of the airbox completely to seal it off, the bottom part is sealed by the weather stripping.

 

[KEITH KRAUSE]

Well, going by your latest reply, it sounds like the popping is easy to live with and goes away soon enough.
Sounds like you've covered the basics trying to eliminate any popping completely. I would still put a torque wrench on the header bolts to be sure they're torqued correctly. Be sure to back off the bolts a little, THEN torque to spec'. Snug them all down uniformly first, then final torque.
If the popping really is a rich condition, it may be from a combination of slightly richer pilot fuel screw adjustment and normal choke use. I know you said the pilot fuel screws were returned pretty close to their original settings, but they MAY be off just a little on the rich side?? You could try turning them all in maybe 1/4 turn max and see how that effects any popping or other performance. If better and no unwanted side effects, leave them there. If not, you can always turn them back out to where you had them and call it good enough. Just be sure to turn them the right way. I only say this because with the screws upside-down, some people mistakenly turn them the wrong way, even with a mirror.
A quick thought. You're running NGK B8ES or equivalent heat range plugs, correct?
Because it sounds like you've done eveything you should, I'd probably just try those minor screw adjustments and that's all. Unless you can think of something else worth attempting, just enjoy the bike.

 

[wideload]

You're running NGK B8ES or equivalent heat range plugs, correct?
Because it sounds like you've done eveything you should, I'd probably just try those minor screw adjustments and that's all. Unless you can think of something else worth attempting, just enjoy the bike.

yes it is NGK B8ES. I bought it last year and remember getting the one recommended on the clymer manual.

Well thanks for the suggestions. Will torque the exhaust this weekend and try 1/4 turn on the pilot screws.

road it to work this morning and no hesitation at all, My GS singing all the way to work

 

[Can_O_Tuna]

Hey Wide...glad it worked for you... Sorry I did not get back to you sooner. My header was in pretty bad shape ,but it held until skip[ made me do a curb jump in Virginia (long story):shock:.

On a small hole it should hold up until/unless the rot spreads. Glad to hear your running better. Keith really knows his stuff huh? :-D

 

[wideload]

Hey Wide...glad it worked for you... Sorry I did not get back to you sooner. My header was in pretty bad shape ,but it held until skip[ made me do a curb jump in Virginia (long story):shock:.

On a small hole it should hold up until/unless the rot spreads. Glad to hear your running better. Keith really knows his stuff huh? :-D

He sure does. It's holding up fine so far. If the rot spreads I'll probably end up replacing it, 5 years later? [-o<