Suzuki 2 Strokes

I got a new set of cylinders for my GT380 and the new cylinders came without the sris ports. I plugged the case anyway so no issue there but my luck would have it that the exhaust bolt on the center cylinder cracked the housing and needs to be replaced. What differences do the cylinders have over the years and what sort of issues will I run into replacing just one.

Have a look here it may help
http://www.kettleclinic.co.uk/kcforum/v ... php?t=4218" onclick="window.open(this.href);return false;

Two cylinder types #1 72-73 (separate carbs) and #2 1974 and up ganged carbs. The difference is the size of the cooling fins. Look at yours and look at some on ebay: you will see what I mean. There should be no problem changing only one.

When I rebuilt my 77 GT380,the right cylinder was in bad shape so I installed one from a 73 ,I haven't had any problems for 2 years now. If you look you can see the cooling fins extend toward the carbs quite a bit more then the other cylinders, but most people don't notice.

Got it thanks, a new one is ordered. Is there any truth to the difference in porting? Why did ignition timing change over the years and what's the best number to use when building a Franken' motor? Now on to pistons, rods, bearings and seals.

The porting didn't change between years, and ignition timing only changed to avoid holed pistons etc, as I understand it the factory timing specs on the early bikes was over-advanced to give sharper low/midrange response. The pistons never changed from the K model through to the final B models.

what do you mean by Fraken motor?

Timing didn't change too much with respect to degrees: did it?. I think they were all around 24 +/- 1/2 degree? Street riding you want to stay at the 24 degrees. You should be safe all the way to 7500 RPM. The issue is maybe more if the engine runs too hot (air cooled you know). Run the B8se not B7se plugs or B9s for example. You can use a 0.020" gasket AL gasket from T250 versus GT 380 0.040" gasket (stronger mid range).

Use GT550 carbs intake ports have more than enough area for them . Oval widen the exhaust port a 2-4mm. Set EX port height 32mm (careful a clean up will take off this much quickly). They are like 32.3mm. some a little more (mfg tolerances?) . Intake timing is decent stock... 1 mm off skirt may help a tad without hurting 3500-4000 rpm too much (gutless here anyways) . You will have good mid range and power to 8000 rpm and over rev to 9000. With stock ignition run fine tip spark plugs to get this over rev cleanly. Chamfer case side of transfer on cylinder like GT250. Cut off/shorten SRIS pipe in transfer passage to allow max flow (I bet this is controversial).

If you tune for higher the RPMs (e.g. raise Exhaust port) against my advice (unless you have a couple bikes and spare parts) for a mild and sporty street goal, It will only run high RPMs (more power here of course) and crank BE will wear out much much faster. Here you may want to run 20 degrees advance (see 1976-77 GT250 porting/timing) since you will be hanging out in the high rpms all the time, no choice (mild mode is gone) and addicting/exciting. 32 mm exhaust height works well and let the pipe help pull the extra RPMs. 1mm extra off EX and you'll know it

All cases a good 3 into 3 system like JEMCOs - boost power and works over a broad RPM range.

my 2 cents OK maybe 3 cents

I just ment cobbled together from original and eBay pieces for Franken motor, it's an early bottom end and head/ram air with later cylinders now. Ordering the cruzin image pistons and rods/bearings for the crank rebuild that needs to be done now. I'm just looking for a cruise around town bike so I'm not porting or changing anything beyond power Dynamo ignition, individual air filters and Jemco pipes

Sure, Every thing I mentioned makes it a good street bike and some things that don't. If me for street skip the individual filters and run stock air box. Some people think it looks better pods, some don't. Or at least use stock box as a baseline to know it can run be jetted correctly.

let us know what you think of Crusin's Rods and Bearings.

My stock 3:1 boot is petrified and the velocity stack section is all torn up and falling out. The individual pods were the best option I could get onto the carbs with out causing an hour of work to install the stock inlet each time. If jetting is that terrible I can always try to make the stock inlet work again.

Usually stuff on eBay and inexpensive or comparable to good pods

http://www.ebay.com/itm/1976-Suzuki-GT3 ... IL&vxp=mtr" onclick="window.open(this.href);return false;

http://www.ebay.com/itm/Suzuki-GT380-ai ... aj&vxp=mtr" onclick="window.open(this.href);return false;

..
Fraken contributions I proposed
Gt550 Carbs
T250 gaskets


I wonder if this would be cool: take the early stock tri boot and fit it to a cut up early filter... leave just the filter element capped and exposed.. Like the RD boys kinda would look like this

http://hvccycle.net/y-boot-air-filter-k-n/" onclick="window.open(this.href);return false;

The later box would look cool too with kind of two uni pods at right angles to motor

I am not sure how much pods versus stock air box will affect you. Some bikes it little other its a lot. It just time and a pile of jets and needle/jet parts (if here not many options)... you see many guys say I got it tune well accept for bla bla... Also pods so much louder. Yeah I like stock air box and looks like I am not too convincing. But have fun either way, live long a try as many options as possible. be happy

Oh Ivans Performance has jet kits for stock gt380 carbs (later style) he claims awesome. And he used stock air box during his many days of fine tuning ( I know I am being an ass)

Once you truly get pod and jetting working at all throttle positions and each position through full rpm range do tell. I hope it's easy.

Usually stuff on eBay and inexpensive or comparable to good pods

http://www.ebay.com/itm/1976-Suzuki-GT3 ... IL&vxp=mtr" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

http://www.ebay.com/itm/Suzuki-GT380-ai ... aj&vxp=mtr" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

..
Fraken contributions I proposed
Gt550 Carbs
T250 gaskets


I wonder if this would be cool: take the early stock tri boot and fit it to a cut up early filter... leave just the filter element capped and exposed.. Like the RD boys kinda would look like this

http://hvccycle.net/y-boot-air-filter-k-n/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

The later box would look cool too with kind of two uni pods at right angles to motor

I am not sure how much pods versus stock air box will affect you. Some bikes it little other its a lot. It just time and a pile of jets and needle/jet parts (if here not many options)... you see many guys say I got it tune well accept for bla bla... Also pods so much louder. Yeah I like stock air box and looks like I am not too convincing. But have fun either way, live long a try as many options as possible. be happy

Oh Ivans Performance has jet kits for stock gt380 carbs (later style) he claims awesome. And he used stock air box during his many days of fine tuning ( I know I am being an ass)

Once you truly get pod and jetting working at all throttle positions and each position through full rpm range do tell. I hope it's easy.

Vintageman,
As you may recall, I'm a convert to using GT550 VM28 carbs under my GT380 carb top, leaving 550 jetting at stock and its great on my 380B. Its my best fuelling bike of three triples by far.
Intrigued by the thinner head gasket suggestion. Are these easy to obtain these days? Do you have a preferred source?
I have a spare head and was thinking one day I could get it skimmed, but I haven't got around to it and don't know how much to take off anyway.
I currently have a very nice street feel and accept that going more radical is useless if the goal is an all-around usable bike.
Thanks for any advice,
Mike

I looked up the T250 gaskets they look easily avalible still. As for the GT550 carbs there pretty picked over on eBay. What about new generic 28mm Keihin or Mikuni carbs?
I tried the air boot thing like this:

Looked cool but was trying to figure out why the bike ran like crap so putting it on every time was taking an hour plus and a major frustration inducer.

hahahaurugly wrote:I tried the air boot thing like this:

That's Awesome, thanks for showing. but ran like crap it sounds . Jetting needed to be adjusted? You know those RD boys have a hard time too with there Y setup. My RD runs stock box with early OEM filter type (no baffles)

You could use 28mm carbs. and GT550 jetting or GT250A/B jetting.Choke would be a challenge to enable at once. Use early GT550 throttle cable and ganged choke enable method? GT380 carbs work well too, just wait and some decent GT550 carbs will show up

Yeadon_m

Here is an example what I used for head gasket. I think still available

http://www.ebay.com/itm/OEM-Suzuki-T305 ... jp&vxp=mtr" onclick="window.open(this.href);return false;

yeadon_m wrote:I currently have a very nice street feel and accept that going more radical is useless if the goal is an all-around usable bike.
Thanks for any advice,

+1 to that.

I have an extra set cylinders with 2.00 MM OS aftermaket pistons this style

http://www.ebay.com/itm/Piston-Kit-Std- ... tW&vxp=mtr" onclick="window.open(this.href);return false;

and have widen the EX port and raise a tad to 32 mm EX height only and did what I said to transfers inlets and SRIS pipe. Just haven't had time to install. And, my 74 gt380 runs well now.

Little more torque would be nice. but its a 380 so another 300-400 rpm peak be would be fun too.... but I have gone too much and just a screamer so holding at 32mm.