Thanks to Murray (MUZ)

With Thanks to Muz, Without Whom This Would Not Be Here

Wednesday, October 17, 2012

New Triple Clamp

In an earlier post I stated that the top yoke or triple clamp had cracks in it.You can see the crack at the upper side of the triple clamp. There is a crack in the same position on the other side. I have no idea how they got there. I can imagine someone doing one side up too tight, but after cracking it I can't see why they would overtighten the other side. One of the mysteries of motorcycling I suppose.

This came in the mail today.
Brand new old stock, still in the original bag. After fitting this I only have to get the flasher can (on order) and then it's basically roadworthy. I don't want to ride it too much until I get baffles for the exhaust. Unless the bike has been rejetted which I doubt, there is a good chance of it running too lean and damaging the engine. The fuel tap is still leaking. The 'O' ring on the vacuum diaphragm needs replacing however when you get a rebuild kit they don't include the 'O' ring. Seems stupid to me but that's how it is.

Saturday, October 13, 2012


The 380 runs very well and smooth. I thought it was a little noisy and lacked a bit of low down torque. Found the problem, no baffles in the exhaust. Well seeing as baffles are just a bit of pipe with holes I thought they would be cheap. Was I wrong. A set of new ones runs over $350 plus freight. They have to come from overseas so I imagine at least $400.

As I said they are very straightforward things so I'm trying to get the specs and fabricate a set.

Saturday, October 6, 2012

It Goes!!!!

Well I still have a leaking fuel tap, the $40 rebuild kit didn't work. The top triple clamp needs replacing and the blinkers don't work.

BUT It Goes!!!. I have started it several times and got it idling and running. It starts well and runs smoothly, I have taken it out a couple of times and have done 17 miles (the speedo is in MPH) and it runs well. No vibrations and feels good and strong. Well, strong for a 1970's small bike.

I ran up the Tawonga Gap and back. Just taking it easy, this bikes not for riding hard or stupidity just cruising. I did notice that 1972 drum brakes aren't quite as good as modern discs but what do you expect?

I also observed that under acceleration there was a huge quantity of blue smoke behind me. Well I do have the oil pump connected and at the same time I'm running premix so I guess that's ok for the moment. I'd rather have a fouled plug than a seized engine.

I checked the oil pump setting this afternoon......way out, way too much going in. I have set it as per factory now....but it's pouring rain and I'm not going out in the wet. Maybe tomorrow.

I do have a big grin on my face. I need to replace the triple clamp (on order) and the indicator relay and the fuel tap, but who cares? Then a roadworthy and club plates.

I'll get a video and post it in the next few days.

Friday, September 14, 2012

GT380 Gear Selector Problem Solved?

I was thinking about the gear box problem. It was strange how the gear lever had no spring back. So I removed the right hand crankcase cover, and the clutch. There was a spring behind the selector arm but it didn't look right and didn't seem to be doing much but I couldn't remember how it should look. I went to the workshop manual, no use. It had an exploded view of the components but not how they actually fitted together.

Now I took quite a lot of photos of the engine during disassembly and went through them. I came to the one below.

You can see the selector arm and that the spring is tight on either side of a fixed pivot on the crankcase. Mine wasn't like that it was flopping around. I must not have assembled it correctly. So I placed it in the correct position and now the lever springs back to where it should be after changing gear. I'll put it back together today and see if it works.

Wednesday, September 12, 2012

Good News, Bad News

Well i started the engine. Took a little while, the carbys still had minor blockages but more work cleared them. The timing was a bit more fiddly than I remembered even though I had a dial gauge but got that right eventually.

A couple of kicks, IT STARTS!!. Stop engine and check everything again. It starts again, it won't idle but I'll fix that later.

Get bike out of garage, start, engage first gear and off. Beautiful it feels smooth, engage second gear, off we go, smooth and pulls ok.

Engage third gear, didn't engage, try again, NO THIRD GEAR. Back into second and back to the garage. Trouble finding neutral, but get it eventually. Examination shows that the gear lever has lost spring and won't spring back to the original position. I go through the gearbox carefully while the bike is on the centre stand. All the gears are there but because the gear lever isn't returning to the home position they are difficult to engage.

Good News - The gearbox is probably ok.
BAD NEWS - I have to pull the engine out again to see what I have done wrong when reassembling it.

Saturday, August 18, 2012

Engine Back In Frame

Put the engine back together, no problems there. All the internals are fine. Engine back in frame. Battery flat and won't charge. New Battery $60. Fuel in, start kicking. After a few kicks, signs of life, a few more kicks and it starts......on one cylinder. Check spark, good so that means it's the carbys. I'll have to take them off again and check everything again. I must have missed a blockage somewhere when I reassembled them.
Maybe this afternoon

Engine reinstalled in frame, minus carbs

Friday, June 22, 2012


I got the crank back at last $185 for the repairs. The bloke who did it was supposed to order a gasket set and a new piston and little end but he didn't. I've ordered them and they should be here next week. Whilst reassembling things I observed that the nylon gear which drives the points cam was cracked. It probably occurred when the engine seized. I found one on ebay $60, ouch. Oh well.
I'll post some photos soon.

Tuesday, May 22, 2012

Crankshaft is Go

Just was told that the crank has been repaired. Although it took a while the price was good $185. I'll pick it up next week.

Monday, April 9, 2012

Still Waiting

Still waiting. I need only one rod, unfortunately they are only available in sets of three. Now it seems that I will have to buy three. I hope to get the crank back soon.

Thursday, March 15, 2012

Waiting, Waiting, Waiting

The crank is ready to go back together except that the person rebuilding it has been having trouble in getting one rod. All the retailers want to sell him a set of three. He's hopeful that he'll get one in the next week or so.

Till then it's waiting, waiting, waiting.

Saturday, January 14, 2012

GT380 - Oh Oh this is not good.

As I wrote in the previous post, the crank is tight in the cases and No1 appeared to be damaged in some way. So I removed the pistons and split the cases. When I split them the crank stayed in the upper case which is unusual.

The crank was tight in the upper case and wouldn't rotate. Further examination showed that rod No1 was bent.

I then had a closer look at the piston, It was broken and cracked internally.

When I split the cases I observed a lot of oil sitting in the bottom of the crankshaft area. This was unusual but I didn't think much of it at the time.

Looking at it now it seems that I had a case of 'Hydraulic Lock'. I don't know how the crankcase filled with oil. The only thing I can think of is that the oil tank contents had bled slowly through the oil pump and feed pipes and had slowly entered the crankcase over the many years of storage. Then when I've started the engine it has run briefly before enough oil was forced up through the transfer ports into the combustion chamber to fill the chamber with more oil than it could hold. As fluids can't compress the piston has travelled up and at a certain point could not travel further and has come to an extremely rapid stop. The inertia of the crank etc has then caused the connecting rod to bend and the little end to break the internals of the piston.
As can be seen in the above photo the rod has quite a large bend in it. The little end bearing and pin are probably damaged as well.

So now I'll have to get the crank rebuilt. I only need one conrod however they are generally sold in threes and are quite expensive. I'll shop around. I should be able to get a single piston and the bearing. Then I'll have the crank split the new rod installed and then the crank rebalanced. Hopefully then it will all go back together and run ok.

GT380 Engine Removal

I pulled the engine out the other day. I am very curious as to why it stopped.

First I just removed the head, carby's and exhausts to see if I could see what had happened.

No luck so it was off with the oil supply for the pump, electrical plugs, clutch cable, tacho cable, chain and engine bolts. Then onto the bench.

Still couldn't see anything so off came the cylinders.

Now I was getting somewhere, No 1 piston was not moving freely and its rod would not move. No's 2 & 3 were free. I was running out of time so I'll do the rest tomorrow.

Sunday, January 8, 2012

GT380 Carburettors

I have settled in at the new location and have finally got a bit of time to address the GT380. The last post was about the leaks in the fuel tank. I put a liner kit in it. I did take photos and documented the process however in the move I seem to have lost the photos. If I find them I will post them.

Anyway the kit worked well, the tank is fuel tight. The fuel tap has a leak and I must get a kit for it (if possible). When I cleaned the carbys there was a hole in the fuel bowl of the middle carb. I was unable to fix it properly, I made a temporary fix for it. It held fuel but did weep a bit, it was good enough to consider staring the bike.

My info was that the bike hadn't been started since the 1980's, I could be wrong about that. Anyway with the ignition off the engine turned over on the kickstart smoothly. I cleaned the points and sprayed a fairly heavy mix of fuel and oil into the intake ports and turned the engine over a few more times. These engines have roller bearings and as long as they haven't rusted they should be alright with a bit of oil. The engine felt smooth and the compression was ok. I put in a new battery, then put a little premix in the tank. I choked the carbs, turned the ignition on and gave it a kick.

Wonderful !!! It started first kick. It idled for about five seconds then stopped. I tried the kickstart it was locked solid. I didn't try any anything else. I'll pull the engine out and see whats happened. Could be anything. I doubt if it's a catastrophic failure. The engine was only idling at about 800 rpm when it stopped. We were getting ready to move at the time so I haven't touched the bike till now.

One thing I did do was to set up an ebay watch for a bowl for the carby. I also contacted Mikuni and many other retailers and specialists to get a bowl. No luck at all, seems the 28mm Mikunis on that are not even known to exist nowadays. Then I came across a set of three from the same model. They were being sold by a wrecker in Ireland. I only needed the bowl but he wouldn't break up the set, so I unwillingly bought all three for almost $150.00. They arrived a few weeks ago and so I began to pull them apart. I thought I would keep the bowl and restore the rest and on sell them again.

I don't know if that is possible. Externally they didn't look too bad, when I began to dismantle them.....yuck and double yuck. The slides were stuck, which I expected. When I removed the bowls, disaster. They were full of a white crystalline substance. I have seen similar stuff on the inside of carbys before but nothing like this. They are almost full of this crap. I don't know if it's a by product of the breakdown of the aluminium or something else, but it's extremely hard to remove. See Below.

It's amazing the entire bowl is just full of the stuff. It had formed around the float and was extremely difficult to remove without damaging the float. Nothing seems to dissolve it. I'll keep looking for a solvent but if I can't find one it's a matter of a lot of time and patience to remove it. I hope the bowl hasn't got a hole in it.

Here a a couple more photos of the stuff.

I'm going to pull the engine out in the next week or so to see what has stopped inside it. I'll post the process.