About a GP125 engine

[adam-stevens]

i have recently brought a gp125 bucket. i want to change to gearbox oil and i was wondering if anyone knew how much to use and what grade to use??

Cheers

[saxet]

800ml at oil change or 850ml when dry. The manual says to use 20/40.

[adam-stevens]

Thanks bud. Ill change it and see if it runs any better. Another thing what does it mean if when i go to take off and it just wants to die on me?? It revs fine when clutch is in or in neutral but as soon as i let the clutch out it wants to die! any advice anyone??

[TZ350]

i have recently brought a gp125 bucket......Cheers

GP125's are the go..... I would love to see a photo........

[quallman1234]

I gather you bought Coyote's bucket. What was sketchy's bucket before then (and i've seen it do 11 o'clock wheelies so its not that slow!) Good stuff man!

Regarding the dieing when trying to load it up. Someone will come along soon with the proper answers. But to me it sounds like a clogged Jet's and general crap in the carb.
What is very possible knowing how long that's GP has been sitting around. Give it a clean out and she should be running sweet!

I know the bike needs a little bit of work, so make sure its tidy and fully nylon when you come up to Kaitoke for the first time. Gonna come up and watch this weekend?
www.bucketracing.co.nz for more details about bike prep under the resources tab.

Good Stuff! =).

[F5 Dave]

As above. The mixture is too weak. Chances are the pilot jet is clogged. Take carb apart (simplicity itself) & take out the small jet down the hole & blow through it until you can see daylight. Don't poke wire through it, you'll ovalise it. Once that is clear try again. Adjust the mixture screw in if still dies under load. If full-in you need a bigger pilot jet.

[quallman1234]

As above. The mixture is too weak. Chances are the pilot jet is clogged. Take carb apart (simplicity itself) & take out the small jet down the hole & blow through it until you can see daylight. Don't poke wire through it, you'll ovalise it. Once that is clear try again. Adjust the mixture screw in if still dies under load. If full-in you need a bigger pilot jet.

While we are on this subject. I have always kinda of known what jet effect what part of Rev Range, but never confirmed it.

Pilot Jet = for the idle?
Main Jet = for the top end?
Needle = Low/Mid Range?

[F5 Dave]

Ahh, this is where we get in trouble. Depends what type of carb. Mostly on small bikes, 2 strokes almost exclusively you have straight pull carbs (unlike CVs used esp on 4 cl 4 strokes).

So the jets correspond to the throttle position. That takes a while to sink in because the bike may respond seemingly to the revs it is doing, but you must think about the throttle position. So Pilot jet & mixture screw is for throttle closed & opening from closed. Then as it opens you are on needle, & near full on- the main. Of course there is some blending, but changing the mixture screw isn't going to do much for a too small of a mainjet for example.

As a rough guide the mixture screw position should tell you which way to adjust it for richer. If like most 2 strokes the screw is on the airbox side of the slide, turning it 'in' will be richer & out will be leaner. If you run out of reasonable movement go the next size smaller or bigger as required.

If the position of the screw is on the intake side; the inverse as it is bleeding in extra gas rather than air.

[Henk]

I seem to recall.

closed to 1/8 th air screw and slide cutaway
1/8 to 1/4 pilot jet
1/4 to 1/2 needle (Could be 1/4 to 3/4 memory fails)
1/2 to open main

As said there is some crossover from one to the other but this should be where each component has it's major effect.

[adam-stevens]

Thanks everyone!! i just want to get out on the track and race haha!!! all i need to get now is some leathers and a back protector and to tidy up my bike and nylon it!!

[Slingshot]

This might be of some use:
204031204047

[adam-stevens]

cheers mate

[Bert]

Back protector:
http://www.trademe.co.nz/Trade-Me-Motors/Motorbikes/Helmets-clothing-footwear/Other/auction-282869422.htm

[bucketracer]

GP125's are the go..... I would love to see a photo........

Me too......................we just love those GP's

[adam-stevens]

i have taken the carb apart and cleaned it all throughly and it still just wants to die when i let the clutch out. im thinking that it might be the clutch?? Where might the clutch be?? i cant really think what else it might be!!!!

[F5 Dave]

The clutch is under the seat, that's not it.

OK so let me guess. You've removed the air filter haven't you? The carb will need bigger jets. Go 2 sizes up on main & see what it's like. Wind the mixture screw in most of the way in while you are there.

ESE guys might have a better starting point than this. Running without filter will cause lean condition that will seize the engine unless compensated for with bigger jets. Any big change will (may) need some compensation one way or the other.

[saxet]

You should be able to suss the clutch without the engine going, just pushing it.
All I can think of is it's out of tune, ignition or carb set up, it's not in first ( yeah i know that seems obvious) or the clutch could have locked up....or a seized wheel bearing, which would be obvious too.

[F5 Dave]

I think he is saying 'wants to die', not like stalls straight off as if clutch locked.

[Slingshot]

Sounds like it's fucked...you should give it to me ;)

[bucketracer]

I think he is saying 'wants to die', not like stalls straight off as if clutch locked.

Clutch plates stuck together? How hard is it to push in gear with the clutch pulled in? Has the rotary valve been cut? massive air leak from the left hand oil seal? If its been a bucket before, does it still have the original carb? Are the jets and float height as per spec's? Is there any compression, whats the ignition timing, and is it CDI or points? Condenser shot?

There were several different carb setups used by Suzuki on the GP's and although, all the std GP carbs we have seen all looked the same the jetting was different, the jets and setups are listed in the Suzuki manual.

Some carb tuning info and theory here:- http://www.dansmc.com/carbs2.htm

On the team ESE's GP's all the mains had to be changed and finished up anywhere from 95 to 110 depending on the bike, but the pilot jet, needle and needle jets were Ok as is, although some of the bikes benefited from enriching the slide.

As there was a flat spot at the quarter throttle position, and that is about the place you use when your just trying to move off.

We enriched the slide by reducing the height of the cutaway. This was done by turning 0.5 to 0.75mm from the bottom of the slides.

Also the height the needle jet stands up in the carb throat has a very big effect on mixture strength or atomization around eighth to half throttle, shorter is weaker and a too short a one accidentally fitted from another carb caused no end of trouble with a major flat spot and was really un rideable. Pic-01

[adam-stevens]

Thanks guys ill try this and hopefully it will work.

[TZ350]

.

From:- http://www.iwt.com.au/mikunicarb.htm

The slide valve affects carburetion between 1/8 thru 1/2 throttle. It especially affects it between 1/8 and 1/4 and has a lesser affect up to 1/2. The slides come in various sizes and the size is determined by how much is cutaway from the backside of it, fig 3. The larger the cutaway, the leaner the mixture (since more air is allowed through it) and the smaller the cutaway, the richer the mixture will be. Throttle valves have numbers on them that explains how much the cutaway is. If there is a 3 stamped into the slide, it has a 3.0mm cutaway, while a 1 will have a 1.0mm cutaway (which will be richer than a 3).

[saxet]

Just to make your life even harder, I have had problems with the ignition windings under the flywheel, LH side of motor.
The only way to test is to replace with another one of the same type.
If you come up to Kaitoke tomorrow ask for Tex on bike 33, and I might be able to help.
Check over your carb first, if it has'nt been fooled with too badly it should be able to be set up without too much grief.