Engine work advice

[azr]

79 GS850G, virtually stock. I went to check my exhaust header bolts and one of the helicoil bolts was broken. The bike has 3 helicoils in her with very small bolts. I want to get rid of all the helicoils, and have some strong solid bolts back in the bike, everything as normal as it can be. I think the best thing to do is remove the head and have a machine shop rethread it for me. What I need is a bit of advice on what to do while I have the head off. The bikes got 40 KM on it now with good compression, 130 across the board. I've been cleaning her up bit by bit and I'd like to do what I can while she's apart. I have no idea what engine work if any has ever been done to it but I do know there is a heck of alot of carbon in there. I'm sure I should put new valve stems in and I'd love to have the block painted stock grey again. So any advice on how to go about all this and what to do while she's apart would be greatly appreciated so I don't regret anything when she's back together again.

[BassCliff]

Hi,

There are many who like the Timesert better than the Helicoil.

I'm just sayin'...


Thank you for your indulgence,

BassCliff

[Big T]

The problem with having a machinst redo the threads is that the result may not be any better than a Helicoil

If you have 130 lbs across the board and it runs good, adjust the valves, clean the carbs and run it

40k, it's questionable whether it would need valve guides - seals, maybe - but old seals would smoke on start up, or us oil

As for paint, I did my head,block and valve cover in VHT aluminum, baked them and had good results - good prep, like blasting, is a must

[azr]

I'm just thinking, 'drill out the helicoils and retap having just the aluminum block with proper thread left', isn't that better? The Timesert does look like a better product that is for sure though. I've got no experience dealing with the aluminum and head bolts. The small diameter bolts that are in three of the helicoils are heating up and snapping in the head, a huge pain I would like to get rid of.

[Steve]

I am not understanding why the helicoiled bolts are any smaller than stock.

If the proper size helicoils were installed, you would be using stock size bolts and should not have any problems.

At 40 KM (is that 40 kilometers or 40 thousand miles? ) you shouldn't have any problems, but since you have the top off and will have all the parts in your gasket kit, it only makes sense to replace the valve seals while you can.

.

[azr]

The bike has 40'000 KMs on it. It doesn't push any blue, start up or any other time. That's what I thought about the bolt size, all I can think is the PO drilled into a busted bolt already in the head and then put a smaller helicoil in. Maybe I can drill out the helicoil and the original busted bolt and get back to the proper size and put a Timesert in.

[Nessism]

Helicoils are thin, I don't understand how an undersize one could be installed into a stripped out hole. Maybe the PO sunk them way deep into the stripped hole? At any rate, I'd use a pick of some sort and dig them out, then either have the proper size helicoil installed or get some Timesert's installed. With 40k KM on the clock it would be a good idea to check the valves/guides for wear and at least replace the valve stem seals.

[Steve]

Helicoils are merely a piece of square stainless steel wire that is coiled into the threads.

Good luck on drilling them out.

.

[old_chopper]

Please do not try to drill the heli-coils out! Follow the advice of Nessism and use a pick to find the end of the insert then a pair of needle nose pliers to pull it out. What size are the bolts in there now? They should be about 6mm I think.

[doctorgonzo]

Please do not try to drill the heli-coils out! Follow the advice of Nessism and use a pick to find the end of the insert then a pair of needle nose pliers to pull it out. What size are the bolts in there now? They should be about 6mm I think.

M8 X 1.25 is the stock exhaust bolt.

[old_chopper]

One reason this site rocks, I posted a guess (wrong) and in 15 minutes someone replies with the correct answer!

[azr]

The bolt in question that I 'thought' had broken off in the head did not. It worked loose as it was too short. It's a 6 I believe, substantially smaller than the stock M8. I touched up the thread a bit and found a longer S/S bolt. I want to tap the helicoil to get the threads working better but I'm not sure if that is a good thing to do or not.

[doctorgonzo]

The bolt in question that I 'thought' had broken off in the head did not. It worked loose as it was too short. It's a 6 I believe, substantially smaller than the stock M8. I touched up the thread a bit and found a longer S/S bolt. I want to tap the helicoil to get the threads working better but I'm not sure if that is a good thing to do or not.

I'd do what Ed (Nessism) suggested. Dig the old heli-coil out and put in a new one, installed properly. Be VERY CAREFUL IF YOU HAVE TO DRILL to install the new heli-coil. a fraction of a mm behind the bottom of those exhaust bolt holes is oil. If you break through you will weep out oil around the new bolt. That's why I have a new head on my G. I THINK stock length is 45mm. It is on a 1000, not sure on an 850.

[old_chopper]

DO NOT run a tap in the heli-coil. If the tap grabs and tries to cut it will spin in the hole and create a real mess for you. If a good bolt won't easily thread into the heli-coil then the heli-coli needs replaced. It sounds like the PO didn't drill and tap the damaged hole correctly for the repair. Nessism said the bolt should be an 8mm. I bet the PO stripped the original then forced a 6mm helicoil in what was left of the original threads. I think the pitch is different from the 6mm and 8mm bolts too. You probably know the answer, fix it right once and be done. Good luck.

[Steve]

One reason this site rocks, I posted a guess (wrong) and in 15 minutes someone replies with the correct answer!

At least you admitted that you were not sure about the size.

What we don't appreciate is someone who posts wrong information with an air of authority.

Some posters have done this, then, when corrected, were really offended.

Not sure that they are still around.

.