74' & 76' GT250 winter projects

[famousseajay]

If you didnt see my info thread i just recently picked up a 74' and a 76' Suzuki GT250 from two different owners. I hope to take a little from both and end up with one kick ass bike for to and from work and around town. I have been ridding or racing motorcycles in way or another for about the past 17 years. But this is my first stab at a full custom vintage ride.


This is how they started...

The 74' This one is the frame donor since it has a title. It ran and rode ok, but something was going bad in the tranny.

The 76' No title, but only 1,700 miles. This one is the engine donor. Ran and rode real good. Actually had a noticeable "on the pipe" feel.

This is the stage i am at now after working on them for a few weeks. Took a bunch of crap off and did a quick mock up with the new clip ons i got in the mail. Mostly to visually see what ideas i have been throwing around in my head for the past month or so.

And the parts counter. I got smart before i started and decided i need to be a bit organized when taking two bikes apart at once.

The next thing on my list is to try and figure out a oil tank/battery box combo of some sort. I want to try and hide as much as i can and leave a lot of negative space in the frame.

 

[zooke581]

I am also doing a GT250. Looking forward to watching your progress.

 

[teazer]

Is the 76 the year in which they made a huge change to the barrels and added extra ports and changed the port timing?

BTW, those clip ons don't look right, but maybe it's the photo fooling me. Clip ons usually droop down at 10 degrees or 15 degrees and those appear to point upwards which would be a wrist breaker.

 

[Streetfighter89]

Man those GT 250's are popping up at the moment! I build one too. I really like this circumstance, because onm other boards its a rare platform to build a cafe.

http://www.suzukicycles.org/GT-series/index.html

The A, B and C models had no ram-air-system, 4 ports, a changed 3rd gear, other carbs, a other crank, other oil-hoses. On the paper it ist weaker in hp than the ram-air-system-equipped GTs.

My one ist a '75 A-Model and has no ramair-system, so is your red one.

The green is a L-Model, ram-air-system, note also apart from the motor changes, the diffrent side covers and the diffrent swingarm. The swingarm with the pegs on is more suitable for rearsets.

Maybe you want to share a kickstand with me just for shipping to germany? In germany none of the GTs had a kickstand due to law restrictions.

Have fun!

 

[famousseajay]

Is the 76 the year in which they made a huge change to the barrels and added extra ports and changed the port timing?

BTW, those clip ons don't look right, but maybe it's the photo fooling me. Clip ons usually droop down at 10 degrees or 15 degrees and those appear to point upwards which would be a wrist breaker.

Streetfigher seems to have all of the info on the different years/models, but the 76' carbs are a lot different and it seems to get up and go a lot better as well.

As far as the clip ons go, i was sitting in the garage the other day looking at them and did realize they are on up side down. oops. : The bars dont have much of an angle so when i putting them on i didnt even realize it. I put them on that way because when i put them on the right way originally they hit the top triple clap weird. Guess ill just have to flip them back over and move them down further on the fork tubes.

 

[famousseajay]

The green is a L-Model, ram-air-system, note also apart from the motor changes, the diffrent side covers and the diffrent swingarm. The swingarm with the pegs on is more suitable for rearsets.

Maybe you want to share a kickstand with me just for shipping to germany? In germany none of the GTs had a kickstand due to law restrictions.

Have fun!

Ya i noticed the green one has the passenger pegs on the exhaust mounts and the red on has them on the swing arm, was planing on swapping the red sing arm over (using the green frame cause i have the paperwork for it) and just running the passenger pegs as my rear sets possibly. Not sure how it will work out, and how to get the rear brake set up.

Streetfighter shoot me a PM about the kick stand. I obviously dont need two....

 

[teazer]

My question about 76 model year was rhetorical. I wanted to see if you knew what you knew and to get you thinking and researching.

The 76 had 4 transfer ports instead of two per cylinder in earlier models and they came with 28mm carbs. Exhaust ports were raised from 32mm to 29.5mm. Cranks and crankcases were changed. Pistons were also different with piston rings pins relocated. Rings were thinner at 1.28mm Vs 1.3mm on earlier pistons.

Timing was dropped from 24 degrees to 20 degrees

Mufflers were different

Transmission was changed to new ratios

Full details in Bulletin GT32 dated January 1 1976. In essence, a 76 motor is more or less completely different to earlier motors and much better starting point.

Some 75 build bikes were sold as 76 GT250A but I think yours is the real deal.

 

[famousseajay]

Found what i think will work out at as pretty cool/unusual oil tank for the bike.

Found it at work. I think it was some kind of float for a big ass valve or something.

Now i just need to figure out what im going to do with the battery. I really wanted to hide it and incorporate it into the oil tank, but that plan has now changed. I also dont want to do a seat hump so that idea is out. Ill figure something out.

 

[drøn]

great project!

now i'll just kick back, let you do he hard work and then use all your great ideas on my gt500.
hope it's cool with you!

 

[famousseajay]

great project!

now i'll just kick back, let you do he hard work and then use all your great ideas on my gt500.
hope it's cool with you!

Haha, thanks! Ya thats fine, just hope most of my "great ideas" work out how i have them envisioned in my head. :-\

 

[famousseajay]

Re: 74' & 76' GT250 winter projects *UPDATE*

After taking about a month off for the Holidays I have dug back into the project GT250's. Havent made a ton of progress, but within the next month or so things are really going to start taking off.

I finally got the engine pulled from the 74' frame so that i can get the 76' engine back in it after shortening, cutting weight, blasting, and paint. Still need to figure out a scheme. I was just going to go with the standard black frame, but Diesel450's CB200, new February bike of the month, has got me thinking a colored frame would look sweet.

Chopped and sectioned the seat pan. A ton shorter and narrower. It will sit about an inch off the frame rails now. I want to make a seat cover, but not sure how its going to work out.

After getting the rear wheel off i fond this weird inner hub type thing on the drive side of the wheel. Its got splines that inter lock into the rubber bushing things on the actually wheel. Is this some sort of early slipper mechanism, or just an easy way so swap wheels in a race setting? I havent wrenched on many drum brake motorcycle wheels so im not sure if this is common or not.

 

[CresentSon]

I have no clues on the wheel, but these little GT's have a sweet frame. I also love the angles of the engine. With a little work this thing could be smokin'. Keep up the great work.

 

[two-smoker]

That's just your standard "cush drive." It's a method of absorbing the shock caused by the slack in the drive line. Not only a comfort feature, but safety, as it can prevent sudden throttle changes from shocking the rear contact patch loose in slippery weather. Pretty much every modern sport bike has a similar setup.

 

[famousseajay]

Re: GT250 *update* ITS ALIVE!

Well this was a long time coming. What started as a winter project turned into a spring project, then into a summer project. But you know how things go... The bike is mostly complete, just a few things here and there that i still want to do, but overall i am very pleased with how it turned out.

The oil tank turned out pretty cool IMO

I took it for a very short maiden voyage after i finally got her fired up. It was short because i dont think the left cylinder is getting oil. It wasnt smoking like the right one was... Ill just have to try and bleed off the air AGAIN! Next on the list of things to do is get the rear sets on the best. As always i am open to constructive criticism/ideas and thoughts. Let me know what you think!

 

[JoeTee]

bike looks great man, maybe i missed something but did you make your own chambers or buy those? If you made them yourself where did you get the info for the dimentions? I would love more info on them, im building a gt380 right now and would like to make my own 3-1 chambers. Thanks man! btw i love the original paint/color.

Joe

 

[Streetfighter89]

Sick chambers!

Can you see any air in the oil lines?

It is possible (and common after that long time) that the right crankshaft seal gets stiff and leaks transmission-oil into the crank-housing, causing a exessive smoke.

Bleeding air at those motors is candy, i don't think that its the problem. Btw be careful with your air filters, it quiet easy to get a hole into those pistons when she is running too lean.

 

[famousseajay]

Re: 76' GT250 *ITS ALIVE*

bike looks great man, maybe i missed something but did you make your own chambers or buy those? If you made them yourself where did you get the info for the dimentions? I would love more info on them, im building a gt380 right now and would like to make my own 3-1 chambers. Thanks man! btw i love the original paint/color.

Thanks man! Actually a fellow 2 smoker on here fabed them up for me. joeschuit (member name) also has a gt250 that he had made a set for, so i asked if you wanted to make me a set. They are his design, he did all of the math and what not, i just sent him my stock headers i cut off. Dude really knows his shit.

Sick chambers!


Can you see any air in the oil lines?


It is possible (and common after that long time) that the right crankshaft seal gets stiff and leaks transmission-oil into the crank-housing, causing a exessive smoke.


Bleeding air at those motors is candy, i don't think that its the problem. Btw be careful with your air filters, it quiet easy to get a hole into those pistons when she is running too lean.

I know there is no air in the line going to the pump from the tank, and i cant really see much on the old lines going from the pump to the engine. Would it be horrible to start her up and just crack the banjos at the engine just to make sure? I figured if there was still air in those lines it would eventually push out...??




I just picked up some larger jets 130, 125, 120 (up from stock 112.5) from the local speed shop that im gonna start with. I figure start withe the 130's and wait for fouled plugs and work back down??

 

[famousseajay]

Re:GT 250 was alive, but then died.


OK, so i guess i was wrong and the stock jets are 92.5, not 112.5. So i tried the 120's and a new set of plugs. Doesnt want to run at all. Fired a few times, but never ran. So im thinking way to rich? Pulled the plugs a few times and they were always wet.


Im new at the whole "tuning" thing. Any info is appreciated. ???

 

[Streetfighter89]

In Idle, pushing the oil pump by hand to full throttle the air is pumped out in about 5 seconds.

Best jets are 102.5, needle clip second position from above, everthing below is too lean. Plugs must be NGK BR9ES.

If your right crank seal is fucked up, so the left one is too, causing too much air getting into the left cylinder, then its running way too lean and you hole your piston. Watch for those probems with the seals.

 

[famousseajay]

Best jets are 102.5, needle clip second position from above, everthing below is too lean. Plugs must be NGK BR9ES.
If your right crank seal is fucked up, so the left one is too, causing too much air getting into the left cylinder, then its running way too lean and you hole your piston. Watch for those probems with the seals.

Thanks for the the info streetfighter. Im headed to the shop tonight to get more jets. NGK's website called for just the B9ES plugs, no R. So thats what i bought and was trying. Whats the R, resistor? Is there a big difference between the two?

As far as the crank seal goes... How can i tell if its messed up? Just keep an eye on constant smoke from the right cylinder? Thanks again! ???