Getting some helicoils done

[xwhatsit]

Allo,

Traced my oil leak down to an inability to properly tie down the valve cover because of some shot threads in the head. This wasn't a problem before, but I suspect there's some warpage that's gone on somewhere since the seize. I will try some silicone sealant first, but if it doesn't stop the clouds of smoke emanating from the mill, then I will get these helicoils done quicksmart (they should be done anyway).

Questions:

1. Where's the best (read cheapest, without being a waste of time) place to have some threads put into my aluminium head in Auckland?
2. I really really want to leave the head attached to the barrel (don't want to buy new gaskets, take out cam shaft, etc). Can I leave the head attached while they do the work?
3. Ballpark estimate of cost?

Thanks for the responses.

[hmmmnz]

basically you'll have to remove the cover as you have to drill a larger hole for the helicoil,
i would just do it yourself, its not that hard as long as your not the rip,shit and bust kinda guy,
you shouldnt have to replace the gasket unless it rips when you pull off the cover, really if its leaking you should spend the $20 to get another anyway,
the last helicoil set i bought cost me $50 and that came with all the bits to do the job(except the drill bit) and about 8 helicoils
if you were to get a shop to do it and providing they dont have to pull the engine out to gain access to the top of the head then you are probably looking at the $50 to $80 mark
have fun

[xwhatsit]

Yay! Somebody replied!

I suppose I could do it myself -- although with me I must always remember I have a huge capacity to stuff up even the most simple things (like fitting a camshaft -.-'').

$50 doesn't seem too bad. When you say pull off the cover, you mean the valve cover, not the cylinder head? I'm not fussed about pulling off the cover, I was planning on doing that -- there's no gasket on the cover, so it's not a worry. What I don't want to do is pull off the cylinder head (where the threads are), as that means new head gasket, pull off camshaft (pain in the arse).

Thanks for the reply.

[hmmmnz]

where exactly is it leaking??
between the top of the head and the rocker cover,
or lower down, between the bottom end and the lower part of the head??
if its there then you'll have to pull the head, if its just the rocker/valve cover (top cover) then just that,
post a photo

i am guessing its a dohc engine and not some old skool push rod engine,
what bike

[hmmmnz]

[imdying]

The CB is the perfect bike to experiment with... give it a go yourself. The skills you'll pickup through practice here will be of use later

[boostin]

Im sure you could give it a go yourself, as long as you are handy with a drill and can keep it true when drilling out the old thread. Then its just a matter of tapping the new one, and screwing in the coil.

If you dont mind the road trip you can bring it over to us at Jennings Engineering. We are working from home over in Albany. Specifically cylinder head specialists, but also to alloy weilding, and other general engineering.

We stock and sell a range of helicoils and helicoil kits, give us a call if you want to talk about it.

Jennings Engineering 4159245

Thanks,

Paul

[xwhatsit]

where exactly is it leaking??
between the top of the head and the rocker cover,
or lower down, between the bottom end and the lower part of the head??
if its there then you'll have to pull the head, if its just the rocker/valve cover (top cover) then just that,
post a photo

i am guessing its a dohc engine and not some old skool push rod engine,
what bike

Hehehe, no pushrods here. Yep, it's leaking in the top arrow you pointed out, between the head and the rocker cover (I called it a valve cover, that's just what the Haynes says). So I'll just pull the rocker cover, nae sweat. Want to see what that camchain tensioner is up to after a few kms anyway.

@imdying: Yep, this bike has been quite the learning experience! Although sometimes I'd just prefer to be able to ride it instead of catching the bus, lol.

@boostin: I'll keep you guys in mind. Won't be attempting this until after next week, I'd say -- got to go to court . Jury service is ghey.

[xwhatsit]

That bottom arrow is actually between the barrel and the crankcase -- there was a tiny amount of leakage from there when I first got the bike. Found out why when I pulled the barrel when I did the rebuild, the base gasket was in about four pieces. Apparently a common problem with these engines -- perhaps why in the gasket set I ordered there were two base gaskets?

[vagrant]

The older XL's and Xr's used the same/similar engine, and mine leaked from the rocker cover. Turns out the frame flexes a little bit when landing jumps. The top engine mount is on the rocker cover, so landing a jump would pull on the rocker cover and cause a leak.
The solution was to either remove the top mount brackets completely, or to put a smaller bolt thru the holes, this would still give a clmaping efect to the mount, but with a bit more play in it.
They don't have a gasket in there because the head and rocker cover are machined as a set for the camshafts, and a gasket would stuff up the clearences.

[xwhatsit]

Wow! Would never've thought about the top engine steady causing problems. Not doing many jumps myself lol (apart from the massive pothole I hit in Northcote on Sunday which caused my glued-up speedo to become unglued once more). Really that top steady is just to stop sideways movement, not up and down, so the smaller bolt trick would do the goods.

I know the bearings are in the head and the rocker cover, and work together -- but why is this different from any other bike with a rocker cover gasket? Surely they're just machined to take care of the width of the gasket, like you do with a head gasket (that can't be out by much, either). Is it a side-effect of the plain-metal bearings which don't have shells? My next bike is going to have replaceable shell bearings everywhere

[vagrant]

Other bikes with rocker cover gaskets have a seperate clamp or plate to hold the cam(s) on top of the head. Honda "cheated" and used the rocker cover for two jobs. If you take the tacho drive off the side off the head, you can see your cam, and how they drilled and machined the bearing surface. As such it doesn't even have bearings in the normal sense of the word. It also means that they are a matched set, you can't get away with replacing one with out the other.

A gasket, even a thin one, relies on it being compressed to seal the gaps between two surfaces, and because it compresses, the running clearance between the cam and head can change. Too loose and the cam will rattle and bounce, destroying the bearing surface. Too tight and there is no room for oil, same result.

[xwhatsit]

Other bikes with rocker cover gaskets have a seperate clamp or plate to hold the cam(s) on top of the head. Honda "cheated" and used the rocker cover for two jobs. If you take the tacho drive off the side off the head, you can see your cam, and how they drilled and machined the bearing surface. As such it doesn't even have bearings in the normal sense of the word. It also means that they are a matched set, you can't get away with replacing one with out the other.

A gasket, even a thin one, relies on it being compressed to seal the gaps between two surfaces, and because it compresses, the running clearance between the cam and head can change. Too loose and the cam will rattle and bounce, destroying the bearing surface. Too tight and there is no room for oil, same result.

Well I'm probably in Mr Honda's bad books then, as I've replaced the head, used that with the original (?) rocker cover, then replaced the rocker cover The cam's not even from a CB250RS, lol.

My head bearings are not very beautiful, and with an unmatched bearing set I don't think my top end is going to be the most quiet, lol.

If it blows up again, I'm sticking a 500 single in it.

[xwhatsit]

Well, bought a helicoil (well, not really the actual Helicoil brand) kit off Enco in East Tamaki (sorry Boostin, would've gone to you but I was nearby at the time, and Albany is quite a commute). ~$56, included ten coils, tap and also the drill bit, which I was pleased about. Good guys there, helped me out even though I couldn't find the front door and wasn't sure exactly what size I needed (the looked at the bolt I gave them and confirmed it was a metric 6mm with 1mm pitch (?).

Again, enlisting the help of my uncle, worked out which bolts needed fixing, marked them off in the Haynes manual, and ended up dropping the engine out of the frame to get clearance for the drill (better than pulling off the cylinder head ). A surprisingly simple process. What was very interesting, though, was that there were some threads that had already had coils put in, but had still stripped. I was worried that you can't coil a thread twice, but apparently you can -- pulled the existing coils out with some pliers, drilled (nothing much came out), then tapped (again, not much swarf). However the coils wound in fine and held perfectly when the bolts went in.

Of some worry was the fact that two of the threads, which are supposed to be oil sealed with a washer, were inaccessible because they went so deep. Unfortunately they had to be left as is, however we put some sticky shit on the threads and the heads of the bolts in an effort to keep them sealed.

How many threads? Well out of a packet of ten, there are two coils left . Hopefully that will keep the rocker cover watertight now. Haven't fired it up -- waiting for said sticky shit to dry, and need to do all the boring stuff like tanks and seats and plug the electrics back together.

Thanks for all the help, it's much appreciated.

[xwhatsit]

Well I'm quite pissed off. After a trouble free day (yesterday), with not so much as a speck of oil, I wake up early so I can ride to Piha on my way to work (quite the detour, lol). First of all, although the bike starts (in normal bump-start fashion), there is absolutely no electrics. No horn, no dash lights, no indicators, nothing. Plenty of battery. So I kill the engine, dismantle almost all of the electrics, and then inexplicably they start working again. No idea.

Next thing I discover as I pull over to the side of the road just before Titirangi, is three Triumph (classic Triumph) riders, one who says he needs a trailer. I don't make much sense when I talk to them, as I'm on such a high from the twisties so far, but they laugh when I bump start the bike down the hill, but sadly also point out my bike is leaking oil and smoking .

It looks like it's coming out of those two un-helicoiled threads. Seems that the sticky shit only held up for so long, but not a high-rpm blat out to Piha (I really need another gear, or to fool around with sprockets). What are my options here? The reason those holes weren't coiled was that the thread went extraordinarly deep into the cylinder head, and there was no way you could get the drill and tap in there. One thing my uncle mentioned was that you could almost just put a coil in at the top (there's plenty of meat, I think) and use a shorter bolt.

Thanks again guys. Mum reckons my bike is getting jealous from the attention I give my girlfriend and she wants me to take her to pieces again and again. I'm glad my real girlfriend isn't this needy.