GT380 questions

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JonnyAstro
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Joined: Sat Apr 06, 2019 7:26 pm

GT380 questions

Post by JonnyAstro »

Hi Everyone.
I just bought a comprehensively-restored GT380L (1974 US import). Very pleased with it!
Mechanically and cosmetically it seems to have had everything done, (there are lots of receipts), and it starts easily and runs nicely, (given that I'm running-in the 1st-oversize pistons so only going to 4krpm so far).
But as I'm getting to know the bike I'm noticing a few details that were perhaps "overlooked"...Most are trivial, but I've noticed that the rubber boots on the carbs, especially on the centre cylinder, are a bit ropey. Do these boots just keep the dust out or are they part of the vacuum section of the CV carbs?
I've ordered replacements but fitting them seems like a b*gg*r of a job, and I'd rather leave it till the winter so I can just ride it for now. But if necessary I will of course attend to it! It idles nicely enough, and the plugs all look a nice colour, by the way.
Any advice welcome!
Jonny
barney01
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Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT380 questions

Post by barney01 »

Hi Jonny
Welcome to the forum. I believe it is possible that air can and will get into the carbs. IMHO It is probably better to replace them before taking the bike too far on the road as it will possibly cause a lean mixture and possible overheating.
NO SMOKE .......NO POKE
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Alan H
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Joined: Fri Aug 05, 2011 6:38 am
Location: Wombwell, Republic of South Yorkshire

Re: GT380 questions

Post by Alan H »

They aren't cv carbs on the air cooled triples. They have proper carbs unlike the later 750s.
To check the rubbers, start the engine and spray carb cleaner around the rubbers (in small 'squirts') - if the engine revs change, they're leaking.
Proof that four strokes are over complicated
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slosher
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Location: Walsall,Black Country

Re: GT380 questions

Post by slosher »

Welcome to the forum :)
Only the boot on top of the carb's will need to be air tight, the other one that covers the pivot joint on the bar is loose anyhow ;)
GT750L
GT550L
TL1000 97s
T140V
Loctite Trained Engineer :lol:(since having the Bonnie)
JonnyAstro
Posts: 12
Joined: Sat Apr 06, 2019 7:26 pm

Re: GT380 questions

Post by JonnyAstro »

Thanks everyone - I appreciate the advice and will investigate further. In the meantime, a couple more questions, if I may:

1/ The rebuilder has set the CCI oil pump a bit on the oily side - delivering more oil than the correct setting would.
To me this seems a sensible precaution for a newly-rebored motor - I'm minded to leave it for a couple of hundred miles then set it correctly.
Or is there a good reason to correct it ?

2/ The tank and side panels have been nicely repainted in Candy Rose, but for some reason the original badges have been put back on the tank, which are "sort of OK", but kind of let the cosmetics down a bit. I've found a set of the correct badges for 1974 with the push-on fixing (there are no screws), so I'll probably replace them. But how to get the old badges off? Just lever them gently, being careful not to mark the nice new paint? Or is there a trick?
Do the new ones just push on or do I need to change the fittings?

Jon
crazy4557
Posts: 550
Joined: Sat Dec 07, 2013 1:24 pm
Location: Lymington, Hampshire

Re: GT380 questions

Post by crazy4557 »

Some tanks will have brackets for the badge to screw to or can be a push fit with lugs on the back of the badge, others have nothing so you need to ascertain what you have. Once you know you then need to get the appropriate badges, it's not as straightforward as you imagine.
Be careful removing the old one's with that new paint.
1976 GT550A in black
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canaletto5
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Location: Derbyshire

Re: GT380 questions

Post by canaletto5 »

JonnyAstro wrote:Thanks everyone - I appreciate the advice and will investigate further. In the meantime, a couple more questions, if I may:

1/ The rebuilder has set the CCI oil pump a bit on the oily side - delivering more oil than the correct setting would.
To me this seems a sensible precaution for a newly-rebored motor - I'm minded to leave it for a couple of hundred miles then set it correctly.
Or is there a good reason to correct it ?

2/ The tank and side panels have been nicely repainted in Candy Rose, but for some reason the original badges have been put back on the tank, which are "sort of OK", but kind of let the cosmetics down a bit. I've found a set of the correct badges for 1974 with the push-on fixing (there are no screws), so I'll probably replace them. But how to get the old badges off? Just lever them gently, being careful not to mark the nice new paint? Or is there a trick?
Do the new ones just push on or do I need to change the fittings?

Jon
Hi

Gently work a plastic spatula under the badge just off the centre and work it back and forth slightly to free one end of the badge. Move the spatula to the other side of centre and do the same. Just repeat until the badge is free enough to lift away. You will find tiny captive nuts inserted into the badge mount holes. If your painter was on the ball they may have replaced them with new ones (I always do ;) ) so you can just relocate the new badges. Otherwise, you might need to replace them

https://www.discountbikespares.co.uk/pr ... gt125-re5/

Kev
barney01
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Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT380 questions

Post by barney01 »

With reference to your first oil pump question. IMHO you should set it as it should be . It's okay to start with but the idea of running in the motor is so that the pistons,rings and barrels wear together but if there is too much oil this may not happen. The other thing to consider is that over oiling will affect the mixture in the cylinder as fuel is also used as a cooling aid.
NO SMOKE .......NO POKE
JonnyAstro
Posts: 12
Joined: Sat Apr 06, 2019 7:26 pm

Re: GT380 questions

Post by JonnyAstro »

Thanks to all respondents - all very helpful - Here's another one for you...!
Having said in the first post that it starts easily, I need to qualify that:
It starts first or second kick from cold with the choke on. It sometimes fluffs a bit as I tweak the twist grip, but soon settles down and after about a a minute I can take the choke off and it idles nicely at about 1200rpm.
Likewise if I stop briefly it re-starts when hot really easily.
But a couple of times recently it has been really difficult to start when "half warm", after say a half-hour break. Tried with choke on and off, doesn't seem to make any difference. After LOTS of kicking it has started, and then ran fine.
Any ideas? Should I try "half choke" or something?
Ignition is electronic "Accent". Plugs are BR8ES - manual says B8ES for my "L" model but interestingly B7ES for all other models. Should I try B7ES? Does the "R" (with extra resistor) matter?
Jon
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Alan H
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Location: Wombwell, Republic of South Yorkshire

Re: GT380 questions

Post by Alan H »

If you have resistor plugs AND resistor caps, you have twice the required resistance and will have a weak spark.
Proof that four strokes are over complicated
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