Thinking about buying a GT380. Had a couple of questions.

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ksluna
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Re: Thinking about buying a GT380. Had a couple of questions

Post by ksluna »

Hey guys well actually it looks like there is a high chance of me buying the GT380.

Doing as much research as I can and plan on buying a service manual and finding one online.

Being new to 2 strokes, I'm just gonna dive in and learn as I go. What are things I can do to keep the bike turn-key?

As I understand, you never change the engine oil in 2T bikes, you just top off and fill up as necessary. But you do change the gearbox oil. How often do you change this? What are some things I need to look out for constantly to make sure the bike will be in constant good shape?
Zunspec4
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Re: Thinking about buying a GT380. Had a couple of questions

Post by Zunspec4 »

ksluna wrote:Hey guys well actually it looks like there is a high chance of me buying the GT380.

Doing as much research as I can and plan on buying a service manual and finding one online.

Being new to 2 strokes, I'm just gonna dive in and learn as I go. What are things I can do to keep the bike turn-key?

As I understand, you never change the engine oil in 2T bikes, you just top off and fill up as necessary. But you do change the gearbox oil. How often do you change this? What are some things I need to look out for constantly to make sure the bike will be in constant good shape?
Hi ksluna,

I am sure you won't be dissapointed with a GT380, they are fun bikes when ridden to their strengths.

Oil- The lubrication for the crank and cylinders is "Total Loss" and is provided by the Suzuki CCI direct injection system and is very effective. No need for mixing oil with the petrol, just keep the injection oil tank topped up with your favourite 2-st lube. G/box & clutch oil is seperate and should be changed approximately every 5000 miles (give or take).

Regular maintenance is basically no different to any other bike. Keep the points in good condition for best performance etc.


Cheers Geoff
ksluna
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Re: Thinking about buying a GT380. Had a couple of questions

Post by ksluna »

Do you have any 2T lube recommendations? As a follow-up, how often should I expect to top it off? Every fill-up?
sportston
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Re: Thinking about buying a GT380. Had a couple of questions

Post by sportston »

Use any good quality synthetic based 2T oil. I prefer Castrol as it is readily available and of very good quality. Don't use mineral oils. If you must use mineral based oils you cannot mix them with synthetic oils, they react and turn to jelly and can clog your oil lines.
You don't have to top off every time you fill up but keep an eagle eye on your oil level. Running out of oil has disastrous consequences.
Craig380
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Re: Thinking about buying a GT380. Had a couple of questions

Post by Craig380 »

No need to buy manuals, just go here:

Factory service manual: http://www.oldjapanesebikes.com/mraxl_G ... /index.php" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Owners manual: http://www.oldjapanesebikes.com/mraxl_G ... /index.php" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

There are parts manuals etc there too.

As Sportston said, use any quality semi-synth 2-stroke oil that meets the JASO FB or FC standards (it will say on the bottle). It must be an injector oil, not a 'premix' oil. You should check the oil pump setting, as per the manuals above, it's an easy job and once you've checked & set it, it almost never needs checking again. Reckon on about 200 miles per pint of oil.

The gearbox takes a 10W40 motorcycle-specific oil for 4 stroke engines. Don't worry about the brand, just use a bike-specific 4-stroke oil. It takes 1.5 litres. Change every 3,000 miles.

Ignition timing and breaker points should be checked every 1,500 miles or so, do NOT do this by following the owner's manual, it's completely wrong. NEVER, EVER turn the engine using that convenient-looking nut at the end of the points cam, you risk breaking stuff.

Any questions, just ask us, and enjoy your new ride!
1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed
ksluna
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Re: Thinking about buying a GT380. Had a couple of questions

Post by ksluna »

Craig380 wrote:No need to buy manuals, just go here:

Factory service manual: http://www.oldjapanesebikes.com/mraxl_G ... /index.php" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Owners manual: http://www.oldjapanesebikes.com/mraxl_G ... /index.php" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

There are parts manuals etc there too.

As Sportston said, use any quality semi-synth 2-stroke oil that meets the JASO FB or FC standards (it will say on the bottle). It must be an injector oil, not a 'premix' oil. You should check the oil pump setting, as per the manuals above, it's an easy job and once you've checked & set it, it almost never needs checking again. Reckon on about 200 miles per pint of oil.

The gearbox takes a 10W40 motorcycle-specific oil for 4 stroke engines. Don't worry about the brand, just use a bike-specific 4-stroke oil. It takes 1.5 litres. Change every 3,000 miles.

Ignition timing and breaker points should be checked every 1,500 miles or so, do NOT do this by following the owner's manual, it's completely wrong. NEVER, EVER turn the engine using that convenient-looking nut at the end of the points cam, you risk breaking stuff.

Any questions, just ask us, and enjoy your new ride!
Thanks, I just looked at some of your links. It says 20w/40 for the transmission oil. I'm assuming that info is outdated and members on this forum have found that 10w40 is better for the gearbox? Should this oil also be synthetic?

Also, another noob question, do 2T oils not have different viscosity like 4T engine oils? I'm looking at these two
https://www.amazon.com/Castrol-Power-TT ... B001KOHX0U" onclick="window.open(this.href);return false;
and
https://www.amazon.com/Royal-Purple-Per ... jector+oil" onclick="window.open(this.href);return false;
which I'm assuming both would work fine for the GT380.
Craig380
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Re: Thinking about buying a GT380. Had a couple of questions

Post by Craig380 »

A 10W40 4-stroke oil is fine for the gearbox but it MUST be a bike-specific oil. Many car oils have friction modifiers which can cause clutch slip. Any semi-synth 4-stroke bike oil of 10W40 viscosity is fine.

2-stroke oils are divided into two types - injector, and pre-mix. Just use oil that states it's for use in injection systems. And remember keep the oil tank topped off: as said above, running out of 2-stroke will kill the motor. Oil and regular oil checks are cheap, engine rebuilds are expensive!
1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed
Zunspec4
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Re: Thinking about buying a GT380. Had a couple of questions

Post by Zunspec4 »

Both of those 2-st oils would be fine. Others may have a different view point but I think our vintage of 2-st's would run fine on cheap weed wacker oil from the local supermarket. However a decent semi-synthetic or mineral oil formulated for motorcycles will also have fringe benefits (other than lubrication) such as low smoke, cleaner burning etc.

Cheers Geoff
ksluna
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Re: Thinking about buying a GT380. Had a couple of questions

Post by ksluna »

When topping off the oil, how low do you guys generally let it go before topping it off? I just don’t know if I should keep it at a constant “full level” or if it’s ok to let it go to the lower end of the dipstick before filling it up.

Thanks for all the help, guys. I was telling my gf last night I really liked the community in this forum and surrounding this bike which is one of the reasons which made me sway and choose the GT380
karl pa
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Re: Thinking about buying a GT380. Had a couple of questions

Post by karl pa »

It is ok to let the oil level drop to the lower end of the dipstick, but I left one go dry and ended up pushing the bike along the side of the road with a locked up engine. :oops: luckily it was only a yamaha :) now I keep them at full level, checking them often.
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
ksluna
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Re: Thinking about buying a GT380. Had a couple of questions

Post by ksluna »

In this thread as well as a lot of other reviews and sources on the GT380, I've read that the middle cylinder is prone to seizing. Besides making sure the oil is always at level and ensuring basic maintenance, are there other steps I can do to prevent this?

The engine on the bike I'm buying is completely rebuilt, so I don't expect to have to rebuild the crank any time soon at all.

Just covering all my bases! I want this bike to last a very long time and want to do everything I can to ensure that, but I also intend on riding it hard!
Craig380
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Re: Thinking about buying a GT380. Had a couple of questions

Post by Craig380 »

That "middle cylinder seizing" is an old wives' tale, and you can safely ignore it as such. Suzuki ensured that the middle cylinder has a huge amount of cooling fin area, and you have the Ram Air cowling which is designed to keep the cylinder head cool.

The things that cause 2-stroke engines to seize / hole pistons are:

- running out of 2-stroke oil
- incorrect ignition timing (ask if the builder fitted an electronic system to replace the factory breaker points, I would think it's likely they have done)
- weak fuel mixture at wide throttle openings

The bike you are buying has aftermarket air filters and expansion chambers. The builder has probably / hopefully altered the carb jetting to suit the modifications, but ask him about that. Ask if the bike has had any dyno time to check the fuel mixture is right.

What I'm saying is, don't assume the previous owner has done the right thing. Even though the bike looks great and has obviously had a lot of time and effort spent on it, it may still need the carb jetting dialling in properly before it is used to its full potential. 2-stroke engines are fickle, and they can and do perform well enough on a quick 'shakedown' ride, but riding it fast and hard is a different scenario entirely and can expose problems.

I'm honestly not trying to put you off by saying this: I'm just advising you to ask as many questions as possible before you hand over your cash.
1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed
ksluna
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Re: Thinking about buying a GT380. Had a couple of questions

Post by ksluna »

Craig, is adjusting the timing a one-time procedure? Or is it treated as a maintenance item? I looked at previous threads as well as the manual linked in here and it seems a bit complex, but easy enough for a newbie mechanic like myself to do. My question is - how often would this need to be checked? Or do you all adjust it once and that's it?
sportston
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Re: Thinking about buying a GT380. Had a couple of questions

Post by sportston »

ksluna wrote:Craig, is adjusting the timing a one-time procedure? Or is it treated as a maintenance item? I looked at previous threads as well as the manual linked in here and it seems a bit complex, but easy enough for a newbie mechanic like myself to do. My question is - how often would this need to be checked? Or do you all adjust it once and that's it?
Adjusting the timing on an electronic ignition system is a one-time thing. Set it and forget it.
BUT, timing on a points ignition system will always go out of adjustment as the points wear. Thus every time you adjust or replace the points you should reset the timing. On a bike with three sets of points it can be a little complicated for a first-timer to get their head around.
I would recommend upgrading to electronic ignition, if it has not already been done. It is maintenance free and more reliable and efficient
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dorT500
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Re: Thinking about buying a GT380. Had a couple of questions

Post by dorT500 »

ksluna wrote:Hey guys well actually it looks like there is a high chance of me buying the GT380.

Doing as much research as I can and plan on buying a service manual and finding one online.

Being new to 2 strokes, I'm just gonna dive in and learn as I go. What are things I can do to keep the bike turn-key?

As I understand, you never change the engine oil in 2T bikes, you just top off and fill up as necessary. But you do change the gearbox oil. How often do you change this? What are some things I need to look out for constantly to make sure the bike will be in constant good shape?
http://www.dansmc.com/mc_repaircourse.htm" onclick="window.open(this.href);return false;"

EDIT: http://www.ozebook.com/compendium/techbuls/index.htm" onclick="window.open(this.href);return false;"
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