1976 gt750A Smoke

Looking for your old Kettle post registration info here good luck!
Post Reply
TwostrokeStu
Posts: 16
Joined: Tue Apr 19, 2016 6:24 pm

1976 gt750A Smoke

Post by TwostrokeStu »

Hi all just after a bit of advice I recently bough a restored GT 750 it has now covered about 300 mile on start up the right cylinder does not run as hot as the other two it has been fitted with electronic ignition also when on the road it really does smoke when I return from a ride there is oil on rear mudguard and number plate but most worrying it is on the rear Tyre, I'am running it on Castrol 1 2T clean burn two stroke oil and wondered with modern oils if it would be okay to adjust oil pump below the alignment marks so it does not get as much oil, awaiting anyone's reply just to add the engine has been rebuilt with new crank / seals / pistons etc.
Roger Ackery
Posts: 3693
Joined: Wed Jul 20, 2011 3:40 am
Location: Sydney NSW Australia

Re: 1976 gt750A Smoke

Post by Roger Ackery »

:cry: Hi,I have the same problem at the moment,but on the left top pipe,mine is slowly getting better & I've done the following after getting advice here :!: :P I have adjusted the oil pump arm back as per attached photo..also switched back to 95 Ron fuel,after using 98 Ron fuel as I thought at the time the fuel may have had something to do with it :idea:
Things have improved a lot..still doing it but not as bad as before ;) In my case I will look at the left carburettor cv diaphragm as its been repaired by me a little while ago, I have a suspicion that it's running rich & what I'm seeing is a mixture of fuel & oil being expelled out the pipe :x If as you say the motor hasn't done a lot of miles ? the crankshaft seals should be o.k. Normally when you get a seal letting go/failing on the right hand side oil will get blown back down the right hand side of the bike..& as you say covering the tyre,mudgard etc? Beside the oil pump is the gearbox breather tube,is gear oil present around this breather .& do you have gear oil in the oil pump gallery,there is a little hole in the crankcase housing for oil to run out of to make you aware that something is wrong :!: (see photo)
Another thing that I'm going to look at on mine,is the SRIS valves to make sure it's recycling oil as designed :idea: By adjusting the oil pump arm you are only adjusting the amount of oil at idle,wide open throttle will remain the same delivery.
Hope this helps,others will advise as well I'm sure :P
image.jpeg
You do not have the required permissions to view the files attached to this post.
Last edited by Roger Ackery on Sun Jul 03, 2016 12:13 pm, edited 1 time in total.
Cheers.
Roger
GT750A.
TwostrokeStu
Posts: 16
Joined: Tue Apr 19, 2016 6:24 pm

Re: 1976 gt750A Smoke

Post by TwostrokeStu »

Thanks for the info Rodger will give it a try just to add my granddaughter has just come back from Sydney yesterday she is an air hostess and she did the Sydney harbor bridge walk, what a job she has got.
Many Thanks
Stuart
User avatar
yeadon_m
Posts: 7401
Joined: Sat Jan 02, 2010 7:10 am
Location: Canterbury Kent

Re: 1976 gt750A Smoke

Post by yeadon_m »

Stuart,
Usually if one cylinder is chucking out a lot of oil, it will be because the check valve on the end of the oil feed line leaks a little. Two solutions which work if you are going to ride it reasonably often: (i) ride it further! eventually after a score or more miles of decent speed, the excess in the bottom of the crankcase will be spat out and it will even up or (ii) remove the SRIS valve in the lower front of the crankcase and allow to drip out whatever has built up. Getting the right and centre ones out is doable with fiddling, I would struggle to get the left one out as everything is in the way with the motor installed.
Personally, I think the SRIS valves and return hose system is a pain and anyone who chooses to plug it at both ends would have my blessing. That said, it works fine for most. The 550 has it but the 380 doesn't. It was intended to reduce smoking on one cylinder by recycling excess oil but it often doesn't.
Good luck and enjoy!
Mike
Roger Ackery
Posts: 3693
Joined: Wed Jul 20, 2011 3:40 am
Location: Sydney NSW Australia

Re: 1976 gt750A Smoke

Post by Roger Ackery »

TwostrokeStu wrote:Thanks for the info Rodger will give it a try just to add my granddaughter has just come back from Sydney yesterday she is an air hostess and she did the Sydney harbor bridge walk, what a job she has got.
Many Thanks
Stuart
Stuart,I did the "Bridge Walk" when I was 19 !!!
Illegally of cause :lol:
Weather has been brilliant here for nearly two weeks,she would have enjoyed the view 8-) hope you figure out the smoking & oil,Mikes suggestion makes sense & I would go with that & see what happens.before getting out the spanner's ;)
Cheers,
Cheers.
Roger
GT750A.
Post Reply