GT750 resurrection

[TNWillie]

Finally got back to working on my Buffalo after a 10 month delay. Last night I reinstalled the pistons and block. Not an easy task without help. I was proud of myself for devising a plan that involved suspending the block using tie down straps hooked to an overhead beam. :) Next up is to determine which of the 3 heads I have available to use and bolt it in place. My goal is to have it running by the end of the month. We'll see.

[Striker1423]

Very cool! I want one lol.

[Evans Ward]

Hi Willie- so this job can be done without taking motor off frame? I've got to do the same thing and Allen Wood is going to help me as he has a homemade cylinder puller. It seized on me last May at Deal's Gap by sludge in oil tank causing a major restriction in the oil line leading to left cylinder.

I may email you offline with a few questions on the repair.

[m in sc]

looks great 

[teazer]

Willie,
That (early 72) barrel is absolutely the best looking of the lot and quite rare now.  Looking good so far.

Evans,
Barrels can be removed and replaced in situ in a stock frame. I usually do that when I rebuild a motor because they are so heavy. You have to take your time lowering the block over the rings, but it's not too hard to do.

If you have to use a puller to remove the barrels, it's easier with the motor out of the frame.  You can still strip off the clutch and alternator and side covers to reduce weight a little.  A complete motor weighs around 180 pounds IIRC.

[TNWillie]

Thanks for the responses, especially the compliments. lol  Kudos on spotting that it's a '72 block. ;)   I consider myself extremely lucky to have been able to remove the block without a puller. Not easy by any means, but it did come apart.
Normally, I would have done this job with the engine out of the frame but I figured I'd make the most of having the forks off for rebuilding and installation of emulators and Progressive Suspension springs. I also wanted to lube the roller bearings in the steering head. Doing it solo was definitely a pita, and required me to use some positions normally associated with Yoga. I knew that supporting the block while making sure the rings were properly located was the hard part. The tie downs made it all possible.
Fwiw, the reason I had to pull the top end was that it had rusted together from setting too long without being turned over. This was the 1st time I'd ever had this happen and came as a real surprise since the bike was in a normally closed garage. Also, it happened in less than 2 months time. I figure condensation from warm and cold cycles was to blame. Still, 2 months?! Wtf!
Also, to make the most of this post and for anyone interested, since I had to clean up the bores anyway, I decided to get the block Nicasil plated, my 1st experience with having this done.
Finally, and excuse me if I've posted a pic of my bike before but I thought I'd attach one for anyone who hasn't seen it. Amazing that I've owned it since '78.

[busa1300]

Very cool! I want one lol.

Have had one under a bench for years now.
Originally was planning a cafe racer...but I have enough 2T troubles already.
Was going to turn it into an end table, but too lazy to strip it down.
Could be available if you want to travel to get it... probably crazy expensive to ship, weighs almost as much as some of my 250's.

[dgorms]

Busa, I'd love to come and poke around under your work benches!

[busa1300]

Busa, I'd love to come and poke around under your work benches!

If I'm home, the garage is always open to 2T addicts 

[TNWillie]

Thought I'd post a pic of the head now that I've spent some time polishing the combustion chamber. I'm hoping to install it tomorrow.

[teazer]

That must be an aftermarket gasket.  See how much larger the bore is compared to the combustion chamber and to the bore.  The best head gaskets come form Cometic.  Order one with 71mm bore.

The large bore gaskets tend to cause detonation.

http://pinkpossum.com/GT750/GT750head.htm  for more info.

[Evans Ward]

That must be an aftermarket gasket.  See how much larger the bore is compared to the combustion chamber and to the bore.  The best head gaskets come form Cometic.  Order one with 71mm bore.

The large bore gaskets tend to cause detonation.

http://pinkpossum.com/GT750/GT750head.htm  for more info.

Richard,

Would the 71mm still be recommended for 1st overbore (0.5mm)? Thanks in advance!

[teazer]

Evans,
That is what I use for a 70.5mm bore.  It leaves a little wriggle room to get it to fit all 3 bores.

[TNWillie]

Thanks for the heads up (pun intended), Richard. I was of the belief that the gasket I've got is OEM. I'll definitely look into one from Cometic.
A new issue has presented itself since I posted earlier today. It involves making a decision between which of 2 heads to use. Here's the deal.
The thermostat housing (cavity?) of the head shown above has been machined down to the point where the thermostat, if used, fits down into the bore and presses against the opening of the fitting directly below it. There is no recess to locate the thermostat and, as such, would essentially float in the bore, being pressed down by the thermostat cover/cap/housing. The other head has the OEM setup with regard to the thermostat. However, the combustion chambers have apparently been filled in (with weld) and reshaped to provide a traditional squish band.
I've attached 2 pics. One shows the underside of both heads for comparison. Please excuse the presence of the thermostat cover.
I would appreciate opinions regarding which head to go with.

[sav0r]

The squish band head is certainly the better head as far as combustion chamber shape is concerned. You might want to measure the volume to figure out what exactly is going on there unless you already have that information from whoever did the work.