1974 GT750 Rebuild

Here you can write about your restoration highs and lows and hopefully final success
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: 1974 GT750 Rebuild

Post by burgs »

Hi
Finished the head studs, and the # 16 stripped bolt hole, bolt refitted and torqued up nicely, still waiting on the cylinder block to be bored :shock: !

Question are the head studs Loctited into the crankcase, they were very hard to get out but didn't notice any residue Loctite?

Burgs
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: 1974 GT750 Rebuild

Post by burgs »

Hi
Finally got the cylinder block yesterday, today ceramic painted and baked them, looking good.
looked at a couple of YouTube clips of fitting the cylinder block and was horrified of what they were doing, anyone got a good way of doing this, I can't cannot remember how I did #1, part of old age I guess :?
I was thinking of spacers to hold the cylinder block square to the crankcase face, fitting one piston into the bore at a time, but that may involve a set of spacers as each piston enter and others fall, don't want the other rings to come out of it's cylinder, I guess it couldn't be much harder than a 360 degree twin, a little bit at a time on each piston.

Wheels, guards, brakes, electrics have been fitted just waiting on engine to be completed, and fitted.
Got to rebuild the carbies, have also got to fit the BS30 jets.

Mudguards are fitted, seat has been recovered, and ready for pick up.

Burgs
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: 1974 GT750 Rebuild

Post by burgs »

Hi
No problem with fitting the cylinder block, middle cylinder on TDC, used overhead crane to hold the cylinder block steady.
#3 piston was tight on the side of the piston pin spacers, found piston had casting flashes left on the inside of the piston, a couple of rubs with a mill file and all good.
The Accent ignition system seems to be held up in transit in Frankfurt since the 10th of April, not a big issue as can run with standard system, just as long as I do receive it.
Seat has been finished and ready for pick up tomorrow.
Phone sopped working so have lost photos :x
Burgs
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: 1974 GT750 Rebuild

Post by burgs »

Hi
Engine is now in the frame, decided to fit the exhaust system, but before doing so I thought I had better remove the baffles and clean them, got the retaining screws out and that is it, they seem to be stuck good and well.
Looking on the internet looks like caustic soda is the way to go, mate tried to clean his Honda tank once and it ended up making it look like a pregnant pig :D .
Other problem was when I went to fit the radiator, the little 90 degree elbow for the hose to the plastic tank broke off in my fingers, only thing holding it on was corrosion.
Bought a new replica radiator from Melbourne $125, it will do until I can source a good original.
The replica radiator looks the goods for a street fighter or classic racer and is stated as being more efficient, but lacks the original look.
I have never had no. 1 over heat at any time with the standard radiator.

Burgs
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: 1974 GT750 Rebuild

Post by burgs »

Hi No.2 Gt750 is running and been on it's first major outing, 3 days of riding, first day started running on two cylinders only, found when on side stand the centre carb was flooding, but when on centre stand all good!
Swapped spark plugs over and all good.
Did this for next two days and all ok.
Removed the carbs at home and found the centre floats had basically collapsed and had some fuel in them, did the boiling water test on the rebuild and all was good, so not sure what happened?
Fitted NOS float to centre carby and measured the float height with the gasket in place and it measured 27.6mm, as spec checked outer two and all good.
Decided exhaust system was past it and ordered a Delkevic system for the M, A and B, told the stands would be an issue but the part numbers are the same for the earlier models, fitted the left-hand side and no problems, right hand side I couldn't get inner muffler on the rear mount, measured the bike mounts they were the same, ended up putting a bigger dog leg in the bracket, this moved the outer right hand muffler up a bit but allowed the inner muffler to be fitted, I also had to add a small dent in the muffler bracket to clear the swing arm, as per the original muffler?
Travelled around 318 miles so far and I am fairly happy with it, it is a lot quieter than No.1 but has a gearbox wine between 50 and 55 mph, 60 and above it is quiet??

Need to go for a test run now to confirm all good.
Best Regards
Burgs
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: 1974 GT750 Rebuild

Post by burgs »

Hi been riding for the last 3 days, did about 1050 km, bike ran extremely well, only problem was the aftermarket blinkers I fitted to the rear, the rubber bulb holders kept coming out of their bracket, from there the bulbs would break, not a biggy, also think I have an earth problem on the blinkers as well.
Cruising speeds were from 65 to 75 mph, must get a kph face for the speedo :)
What I learnt from the ride.
1 bike handles very good all round considering front forks rebuilt standard, rear shockies still original, bumps never really affected the handling in corners and straight line handling still good up to 90 mph plus
2 seems to be revving too high for the speeds so may change gearing as per no. 1 bike, has good acceleration at high speeds though
3 had crank balanced when rebuilt, very smooth from around 55 mph upwards, but vibrates below this speed, have to look at what balance factor was used and see if the vibration can be reduced down lower as you can do with singles?
4 the ride included a good selection of roads, from twisty 25 kph bends upwards, to miles of relatively straight roads with high speed bends 65 to 90mph plus when we got out in the county.

Good time had by us all, mates were on modern bikes, Hondas and BMWs kept up with them no problems when they were in the lead.

Burgs
teazer
Posts: 1035
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: 1974 GT750 Rebuild

Post by teazer »

A lot ( all?) GT750s shake more than we would expect. With a fiberglass seat it is really annoying and in general I think that the lighter the bike is the more it can shake. There's less mass to damp out the vibration caused by a rocking couple - and I don't mean Alan and Steve......

My Dunstall seemed to be worse at around 1500 rpm and as revs rose it smoothed out.
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