Hey from Newfoundland

Posted: Wed Aug 10, 2011 6:39 pm

Hi all I own a '79 cb750k I had to do a lot of work to get it on the road, mostly maintenance that was neglected over the years. The front cam chain tensioner bolt had the housing striped out so I managed to fudge a standard bolt in there and got 1300km out of it till it started getting bad. So I pulled the head and am in the process of going thru the head, cutting the valves, seats and what ever else it will need.

I work at the major automotive performance shop here in Newfoundland. I build both street and strip engines. My favorite thing to build is the strokers, I only have experience with stoking small blocks but to me they are the most impressive. Now that my engine is pulled down I am thinking stoker for a winter project, low budget all cb900 guts. For now I''m looking for a set of cams to drop in and get back on the road and out of the cage.

I'll post some pics when she is back together, I'll warn you now I'm a chopper guy Very Happy

Great site have been studying it for a while now, but now I'm getting serious about this platform and the 90hp I think I can get out of it.

Posted: Wed Aug 10, 2011 7:02 pm

PerformanceRebuilder wrote:

The front cam chain tensioner bolt had the housing striped out so I managed to fudge a standard bolt in there and got 1300km out of it till it started getting bad.

Meaning that it is leaking oil?

Without the proper bolt, oil will always will be a problem. The bolt is two tier. The bottom is 8mm and the top is 10mm and in all that it has an o-ring to prevent oil travel.

Posted: Wed Aug 10, 2011 7:47 pm

That would be the bolt, but it will always leak in my case due to the fact that it has no threads thanks to the previous owner. The hole is being bored out and a heli coil being put in to fix the problem.

Posted: Wed Aug 10, 2011 7:52 pm

PerformanceRebuilder wrote:

That would be the bolt, but it will always leak in my case due to the fact that it has no threads thanks to the previous owner. The hole is being bored out and a heli coil being put in to fix the problem.

Do not use a Heli-Coil. Put a Timesert in.

Posted: Wed Aug 10, 2011 8:12 pm

Not familiar with Timesert I`ll have to check it out.

Posted: Wed Aug 10, 2011 8:21 pm

It is worth the investigation. Heli-Coil's will back themselves out after install. I have seen it myself after I put one in.

Posted: Wed Aug 10, 2011 10:00 pm

Just to tell the other side of the story :

I have installed many heli coils over the years and never seen one back out when properly installed .

Posted: Thu Aug 11, 2011 12:49 am

Getting one "properly installed" in a head in the bike might be a real challenge. I've seen them not just come out before, but come unwound. I think it had probably been cross threaded.

The hole in the head has precious little aluminum to hold the thread replacement. It is not a complete hole all the way around down there. That is part of the problem. A cylinder like a TimeSert will work considerably better in there rather than a coil, IMO.

I like to put inserts in that hole whenever i have one of these heads off just on GPs. Rolling Eyes

Posted: Thu Aug 11, 2011 5:37 am

In regards to cutting the valves and seats, you better know what you are doing and you will wind up with a pile of scrap.

Cutting valves removes the coating and they become soft. Cutting the seats improperly and valves may result it not being able to get shims thin enough to get the proper clearances.

90% of the time the only thing required is laping the valves with some compound to get excellent seals again. Even that causes you to drop a couple of shim sizes most times.

If you have not done it yet, you might want to re-think it.

Posted: Thu Aug 11, 2011 5:50 am

pd750 wrote:

Just to tell the other side of the story :

I have installed many heli coils over the years and never seen one back out when properly installed .

I'm in the same boat. A properly installed heli coil is just fine. I'm sure the Timesert is a better product, but if you have experience installing helicoils, than I wouldn't shy away from them.

Posted: Thu Aug 11, 2011 5:58 am

Welcome by the way!! My in law family are from the Grand Bank and Fortune.

Post up your engine build, I look forward to watching it.

Posted: Thu Aug 11, 2011 10:47 am

Thanks for the post guys. I will have another look at the head but I work in a very good proformance shop and we don't do thing's to make scrap out of them. I will ask our head guy to have another look and see if he agree's. As for the heli-coil we do a lot of these and they work very well, no complaints. I have asked around and timesert's are just not used around here, so I'll stick with the heli-coil for now.

I have family in the Grandbank area as well. Cheers.

Posted: Thu Aug 11, 2011 5:28 pm

After re-reading your post I realize you have the head off. Embarassed

The hole in the head is irregular and has precious little aluminum to hold the thread replacement. It is not a complete hole all the way around down in the hole, it has a void on one side. In fact, if you aren't careful when drilling it out with a hand operated drill, it's easy to get the hole drilled crooked due to the lack of aluminum on one side.

I still say a cylindrical sleeve insert like a TimeSert will work considerably better in there rather than a coil, IMO. I think it will work better without support all the way around the threads.

I have seen other "old pros" reluctance to try these in the past, stating similar tired old logic. Once they do, they are generally bowled over by how much better they really are for some applications, if not most.

When threaded holes are needed in plastic pieces, a similar technique is often used to make a reinforced thread, they don't use coils, which was a pretty good technology when they were invented, and still works, but it's not the 1930s any longer. No, they use a cylindrical sleeve insert.

When I was first acquainted with TimeSerts in the 1980s, a friend of mine had a Kawasaki based N2O drag bike. Cylinder pressure was an issue, and he had a problem with studs pulling out of the case. So he TimeSerted them all, no more problem. I actually own his old nitrous system now.

One other thing, the use of Lok-Tite® is ill advised with a coil. A cylindrical sleeve type insert should have no issue with it though.

http://www.airheads.org/content/view/213/49/

www.timesert.com

And I have no monetary interest at all in either product. Rolling Eyes

Posted: Thu Aug 11, 2011 6:35 pm

I just want to say that I am not the type to think I know it all, nor do I need my ego stroked. I am a sponge for information so thank you again for all the responses. The basic story of this project was low buck all the way. My personal self can not afford to do what my professional self does on a daily basis. That being said I don’t do stupid s@#% that will cost me more in the future. I ran her until the front cam chain bolt had no way of putting tension on the tensioner due to the lack of threads. Then I parked it and pulled the head. With very little cuttings in the oil, a good flush should do it.

I have already shagged it by all accounts seeing as I have drilled the hole to work for the heli-coil. So now I guess I’ll spin the wheel and keep a very good ear and eye on it. But now I can say I’m educated for the next one, for example the other engine I picked up to build as a stroker.

As for the valves and seats, I guess I have to make sure to use the right terms. I have worked as the primary engine re-builder for this company for about a year, I’m still being trained on the head work side of things. When I said the valves and seats needed to be cut, I didn’t necessarily mean ground, cause honestly I still run all that by our head guy. When I did reconfirm he agreed that lapping was the way to go because of the coating . So cheers and thanks for the info.

Posted: Thu Aug 11, 2011 7:18 pm

Well, this thread is just a friendly exchange of information after all. Wink

When stuff is written down in this delayed posting medium, it can be taken weightier than intended, and sometimes the intent and purpose for a post even gets confused. It sometimes presents to make a statement seem much more serious to the reader than what the writer was thinking or meant at the time, and there is no immediate interaction to confirm it before a further reply or even a bunch of replies from elsewhere takes the whole tone of the thread to an entirely different level without any clarity in regards to what was really going on in the first place. And each writer tends to bring their own agenda to the tablet too.

After really taking a second and third look at this thread, I'm convinced you were just saying hello really, and not displaying your horga'hn to seek technical jamaharon Laughing

So WELCOME TO HERE!!! wave

Posted: Fri Aug 12, 2011 5:13 am

Cheers