GS750E Rebuild Update

[Guest]

Ok, I am tackling owning my first bike and my first overhaul all in one season...hold your applause.

Issue #1:

My friend and I cannot get this cylinder block to come off the engine. The Head came off so easily but this block wants to be a PITA...

I have sprayed some PB Blaster around the base gasket in hopes it will work its way free but I am resisting the urge to go ape *explicative* on it and risk breaking something (like a fin or two) so I have stopped for the night.

Does anyone have any further knowledge that I might be able to apply to my stuck block issue?

Plan as it is to get the block & head off and have both inspected by a local shop, since I don't have a great deal of knowledge of such things myself and would prefer not to have to revisit this again if I screw up. With all luck they will inspect the valves / block and find nothing wrong and I can just replace my leaking gaskets and not worry again about this for awhile.


Issue #2:

Discovered that my exhaust has a rusted out hole on the pipe. initial thought was it was just my exhaust flanges not being tight enough to cause the leak but the hole in the pipe says otherwise. My friend and I have taken our share of pictures as we take my bike down since I was a visual aid upon reassembling ... also been bagging and tagging everything to boot. I will upload photo's later of the holein teh exhaust since I am unsure if I want to pay to have a weld fix it ... try to find a muffler in a yard...or simply upgrade my exhaust $$$ ... suggestions?

[txironhead]

Issue #1: while you've got it apart, if the cylinders are still good enough for the factory bore, you're gonna want to hone the cylinders and probably look at a new set of rings. Like you said, you don't want to have to do this again for a while. I'd go ahead and do a valve job or at least lap the valves, too. MAKE SURE you inspect and/or replace the valve seals.

Issue #2: if you go with an aftermarket exhaust, you're going to have to do some carburetor adjustment/rejet. Not saying that's a bad thing, but it does involve more work. You're probably going to tear the carbs apart to clean them anyway, but putting a set of carbs back together and going through the fun (insert large amount of sarcasm here) of rejetting are two totally different things. Trust me, I'm learning this the hard way on a GS750E of my own. Except my bike came with aftermarket exhaust and no airbox, hence the pods. If you can find a good factory exhaust and don't want to mess with rejetting, go that route.

[Kcwiro]

Response to txironhead:

on issue #1:
I was reading that part of my manual and was left scratching my head on it, shop inspection should yield a good result and as you put it with lapping the valves and replacing the seals is hopefully all thats to be done there.

on issue #2:

you are correct on the cleaning of the carbs.... less than fun cleaning but I have a helpful hand at my job helping me out with learning the ins and outs. They were gunked up and enjoyed dumping fuel into my airbox... hopefully the cleaning will do them good and once the engine is ready it'll be good to go. Aftermarket exhausts look ggood and sound great... but the rejetting is meh... I will look at the local yards and see if I can find a decent set of stock pipes...even one would surfice since only one pipe is rusted through.

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then I will move into the pingel mod on my tank and replace that fuel line...then get a stainless steel break line kit....yet more work but fortunately the winter has really just started showing up here so I have tiem on my side for this

[txironhead]

For a good tutorial on cleaning the CV carbs, check this out:

http://www.thegsresources.com/gs_carbrebuild.htm

Full color, step-by-step guide to rebuilding your carbs. I definitely wish I'd had this when I tore my first set apart.

[Road_Clam]

Ok, I am tackling owning my first bike and my first overhaul all in one season...hold your applause.

Issue #1:

My friend and I cannot get this cylinder block to come off the engine. The Head came off so easily but this block wants to be a PITA...

I have sprayed some PB Blaster around the base gasket in hopes it will work its way free but I am resisting the urge to go ape *explicative* on it and risk breaking something (like a fin or two) so I have stopped for the night.

Does anyone have any further knowledge that I might be able to apply to my stuck block issue?

Plan as it is to get the block & head off and have both inspected by a local shop, since I don't have a great deal of knowledge of such things myself and would prefer not to have to revisit this again if I screw up. With all luck they will inspect the valves / block and find nothing wrong and I can just replace my leaking gaskets and not worry again about this for awhile.


Issue #2:

Discovered that my exhaust has a rusted out hole on the pipe. initial thought was it was just my exhaust flanges not being tight enough to cause the leak but the hole in the pipe says otherwise. My friend and I have taken our share of pictures as we take my bike down since I was a visual aid upon reassembling ... also been bagging and tagging everything to boot. I will upload photo's later of the holein teh exhaust since I am unsure if I want to pay to have a weld fix it ... try to find a muffler in a yard...or simply upgrade my exhaust $$$ ... suggestions?

The cylinder is simply "bonded" to the base gasket. Use a plastic "dead blow" type hammer, and give it a few raps. It should break free.

[DimitriT]

Some will wince at my technique for loosening the old gasket but they can be stuck on there pretty good. If the tapping and pulling doesn't work, I pull out a thin putty knife and insert it along the gasket. A couple of light taps with a hammer on the handle and the block will separate. All it needs is a little leverage. So far I've done this on two gaskets and haven't done any damage but YMMV.

Definitely clean the carbs while they're off. If its the first cleaning since you've owned it go through the full cleaning, otherwise just take the jets out and clean out the holes and apply a little cleaner in the passages.

Where's the hole in the exhaust? On the can? I just repaired a hole on the underside of the muffler using a small piece of galvanized metal stock and some JB weld. A hole in one of the headers would get too hot for this. I would look into getting it welded unless the rest of the exhaust is looking like it's falling apart too. Exhausts are expensive and might cause mixture problems if the backpressure is wrong.

[Big T]

Use a small piece of wood with your hammer and tap upwards at the intake and exhaust ports. Be gentle
There are some locating pegs on the top corners of the cases and the block is likely stuck on those. Shoot PB blaster down the corner studs

[Kcwiro]

Where's the hole in the exhaust? On the can? I just repaired a hole on the underside of the muffler using a small piece of galvanized metal stock and some JB weld. A hole in one of the headers would get too hot for this. I would look into getting it welded unless the rest of the exhaust is looking like it's falling apart too. Exhausts are expensive and might cause mixture problems if the backpressure is wrong.

The hitting on it with a mallet has not busted the seal for me and I don't want to over do it and bend something... I'll give it another go later today... I am referring to the base gasket btw ... head came off easies out of all the seals my friend and I had to break

The hole in the exhaust is on the muffler side pictures will explain it better http://www.sigma-gamma-tau.com/gs750/motorcycle_rebuild/IMGP0226.JPG

http://www.sigma-gamma-tau.com/gs750/motorcycle_rebuild/IMGP0227.JPG

second pic is to get an idea of where it is in the big picture

[Dink]

Certainly is a rusthole, you probably wont be able to weld it up. as the metal around it will be very thin. It will almost certainly need to be plated over.

Dink

[Kcwiro]

plated over? I've never seen that done before but I assume your talking about a sheet of metal being wrapped around it then seamed down? Sorry I just am not seeing this in my head... visual aid might be helpful. Would any exhaust system require re-jetting since if I understand them correctly I have a 4 into 2 stock... if I were to replace it with another 4 into 2 would I still require the rejetting? From what I have eyed it looks like the after market 4 into 2 don't have the cyl 2 & 3 cross section ... so that could cause me an issue even with a new 4 into 2 ... am I correct?

More hitting with the mallet has not proven productive (i got all the bolts out for sure...guess it just wanting to fight more) I will give it another shot when I get back in town Tuesday evening using the puddy knife and hope that gets it since I want to get the block and head to the machine shop to get their work done sooner rather than later. See if the added PB Blaster helps loosen it up further.

My work has a solvent tub that the shop manager said I could use to clean up everything before I take it to the shop since I don't want to pay for them cleaning it on top of what I already am asking them to do. Though it certainly requires me to get the thing off the bike first to be able to clean it.

[duaneage]

Find a local welder that can touch that hole up, I would not replace the entire pipe for that.It is not visible so I would clean it, weld it, adn then paint over the welded area with high heat paint. It is far enough from the engine where it won't be too hot and the paint will help keep it from rusting.

My neighbor has a 500 virago and the pipes are impossible to get for it. He welded some really large holes in the pipes and it came out fine. They wanted hundreds of dollars for aftermarket pipes, more than the bike was worth.

[txironhead]

Aftermarket pipes are designed to be less restrictive than the factory exhaust. Even if you found a 4-2 with a crossover, it would still have less backpressure. You may not need a rejet, but you'll definitely need to re-synchronize the carbs and possibly put some spacers under the needles. It'd probably be easier to go with a Dynojet kit.

It looks like the headers are okay, you may be able to just buy a single muffler as the other one looks much better than the rusted one.

[Kcwiro]

Well here is the real kicker... I did not mention that the header pipe and the muffler are welded on as a single piece I did not weld that TPO likely did that why? I have no clue...usually there is some kind of clamp that joins the header to the muffler but apparently this person wanted to forgo that clamp.

This something I can simply just hack through with a saw? Since that would be shortening the header pipe I think I might be SOL.

[txironhead]

Well, you've probably solved the question of how it happened. Likely there was a leak or something that the PO decided would be easier to fix by welding than by fixing it properly. The weld destroyed the chrome (and probably weakened/destroyed internal baffles, etc.) and that led to the massive amount of rust on that muffler.

You may get lucky and find just one side of the exhaust at a junkyard. I did an internet search on motorcycle junkyards and was surprised to find one almost in my backyard that I didn't know about. Of course, I've only been here two years, so that may account for it. Also, on these bikes Ebay is your best friend.

You may be able to hacksaw the pipe off and have someone weld an extention if you find a factory muffler, or you can chop both off and try to modify it to accept aftermarket mufflers, but do both or you'll have an imbalance. With all of the hassle involved, especially since the headers probably won't last that much longer, you might try to find a decent set of aftermarket pipes. You might also look into having a muffler shop use your existing headers, modify them to accept aftermarket mufflers, then Ceramikote the whole setup or paint the headers black with exhaust paint (paint the inside too after a good cleaning) and leave the mufflers chrome. It's an interesting look that I happen to like but it's your bike, your decision.

[Kcwiro]

I see your point on welding the extension and all this extra stuff... I didn't get a pick of the dents that were on the cans of both mufflers... Noticed them first when I was checking the bike out.

My best guess on those is the guy did not want to take the exhaust off like you should and the rear axle nut pushed out and dinted the inside of the pipes.

Would think if I going with after muffler I might just want to take the next step and buy a MAC or V & H ... re-jetting sounds like a bummer but I have them coming apart anyway so I guess its what the hell you know...

looks like I will want to put some money away for replacing the exhaust... from what I have seen on ebay looks like ~$300 for a full aftermarket exhaust and I can just sell the stuff I got if anyone will take it. More work but nature of the beast.

Suggestions on vendors anyone? From what I have read the Vance and Hines stuff might need a bit of dremel to get the fit right? Also guess I should think If i wan to go 4 into 1 or 4 into 2... I'll have to think that over.

Chime in your two cents guys