Suzuki GT250 tuning

[chrisc]

Anyone on here a racer from way back that can share some tuning experience with the X7 GT250 Suzuki?

I picked one up over the weekend which needs more than a bit of a attention. Plan is to get it going properly on the road for a quick hoon around.

I've never seen this type of reed valve assembly before, clearly i'm showing my age here.

314669314670

If you have parts lurking around, particularly the older spoked wheels, send me a message!

Chris

[Grumph]

The X7 can be made to go quite well. Limits are usually cooling - finning is pretty scanty....
Like the LC, the head is one piece so doing the squish is not easy.
Bits are readily available, I reco'd one for a guy here a couple of years back. Pistons, rings,seals,rod kits, mains all ex UK.
From memory, not much change from 2K.

Talk to F5Dave about case reeds, he's the believer....

[husaberg]

Anyone on here a racer from way back that can share some tuning experience with the X7 GT250 Suzuki?

I picked one up over the weekend which needs more than a bit of a attention. Plan is to get it going properly on the road for a quick hoon around.

I've never seen this type of reed valve assembly before, clearly i'm showing my age here.

314669314670

If you have parts lurking around, particularly the older spoked wheels, send me a message!

Chris

Pretty sure they were the same set up as the Rg50 and quite a few others incl the tf125 re the reeds.
Side note I don't think I ever seen one that was not red.

[Grumph]

Pretty sure they were the same set up as the Rg50 and quite a few others incl the tf125 re the reeds.
Side note I don't think I ever seen one that was not red.

Pretty sure there's a blue one comes out with CAMS - but yes, all others I've seen were red.

[husaberg]

Pretty sure there's a blue one comes out with CAMS - but yes, all others I've seen were red.
They probably would have sold alright if the LC had never came out.
Does the RG250 have the same flat reed set up or different? Never seen one apart.

[chrisc]

The X7 can be made to go quite well. Limits are usually cooling - finning is pretty scanty....
Like the LC, the head is one piece so doing the squish is not easy.
Bits are readily available, I reco'd one for a guy here a couple of years back. Pistons, rings,seals,rod kits, mains all ex UK.
From memory, not much change from 2K.

Talk to F5Dave about case reeds, he's the believer....

Yeah machining the head doesn't look like much fun.

I'm pretty keen to get some modern single ring pistons in there. 14mm pin sucks though.

[F5 Dave]

Yeah all Suzuki's had that setup including the 4 strokes. OK maybe not but RMs, PEs, TS, RGs of all sizes. It's a bit of a shitty system. The latter the model the flatter the reedblock.

My X7 had TS125 pistons which takes to 275. Heads cut in two and some porting and skimming.
The cranks like most Suzuki's is barely adequate.

You'd want to rebuild crank from the start and try find some Yam parts to fit. Opens up piston options.

GS550 caliper dramatically improved the brake. GS550 shocks discarded from my old 550 were longer and stiffer and helped ground clearance, steering and despite being rooted were better than std.

Think I saw the old motorcycle mechanics article on the web recently.

Mine was Blue, there was White and Red too. X5s seemed to be black or yellow but they are a bit different. A mate has just done one.

[T.W.R]

Think I saw the old motorcycle mechanics article on the web recently.

.

Have got the 3 issues from May 1980 - July 1980 , basically they took a RD250E & a X7 ( with 8800 miles on it) and tweeked them. The X7 went from measured 17.9bhp @ the wheel to a max of 30.5bhp ; used larger carbs pod filters micron pipes etc and lot fiddling and testing. Will scan the series when I get a bit of time

[husaberg]

Have got the 3 issues from May 1980 - July 1980 , basically they took a RD250E & a X7 ( with 8800 miles on it) and tweeked them. The X7 went from measured 17.9bhp @ the wheel to a max of 30.5bhp ; used larger carbs pod filters micron pipes etc and lot fiddling and testing. Will scan the series when I get a bit of time

I have the one where they went through the design process I will post them as well then.

[chrisc]

Thanks for that lads. Mine is currently house paint blue but was red and will again be red soon enough.

[TZ350]

Anyone on here a racer from way back that can share some tuning experience with the X7 GT250 Suzuki?

Will the next model water cooled RG250 cylinders fit??? if so give me a PM.

[TZ350]

Yeah machining the head doesn't look like much fun.

A few $$$$ and Sketchy with his CNC machine is an option.

[Grumph]

A few $$$$ and Sketchy with his CNC machine is an option.

If you split the head to machine squish - a good option IMO - take the time to dowel head and barrel as there's no positive location on the damm things.

[chrisc]

Will the next model water cooled RG250 cylinders fit??? if so give me a PM.

Now there's a thought! I'm keen to keep it air cooled though, it won't be stressed that much on the street.
Will give you a call anyway Rob

[husaberg]

Try here
http://www.suzuki-gt.co.uk/Reference%20Library%20Page%202.htm
I had already scanned this one when I found this page
I have also converted the 250 shot out.
There is a pretty decent tuning article based on the very quick look I had.

Also in Bells book he goes through the Power Reed system including what happens if you take it to far.

[husaberg]

rest.............

[husaberg]

more of the rest.

[Blackbird]

They are terrific bikes - I bought one for our son to learn on in the 90's but truth be told, it was for me to thrash round the country lanes when he was at varsity. Sold it in the early 2000's. In a strange quirk of fate, one of my neighbours here in Coromandel now has it, together with massive boxes of spares he picked up from Hamilton over a decade ago. It hasn't been ridden for over a decade and I keep pestering him to buy it back but no joy yet. :angry:

Photo of the bike when my lad rode it and I had a K100 RS

[T.W.R]

I have also converted the 250 shot out.


rest.............


more of the rest.

:facepalm: You need to get a job :bleh:
Just scanned off & re-sized all that article :doh:
should run off the Rickman piece further in the June issue for mike's thread :corn:

[husaberg]

:facepalm: You need to get a job :bleh:
Just scanned off & re-sized all that article :doh:
should run off the Rickman piece further in the June issue for mike's thread :corn:

I has a job.
I did only find that one by mistake though

[F5 Dave]

RG barrels would need an alternative water entry if they did fit.

PWK28s would be best carb, can be converted to oil injection easily and used to be available as KR1 carbs from wreckers. Or kx80 fitment new on ebay but more spend.

[chrisc]

Try here
http://www.suzuki-gt.co.uk/Reference%20Library%20Page%202.htm
I had already scanned this one when I found this page
I have also converted the 250 shot out.
There is a pretty decent tuning article based on the very quick look I had.

Also in Bells book he goes through the Power Reed system including what happens if you take it to far.

Husa, thanks man! Your the king of online motorcycle resources!

[chrisc]

Anyone know where I can find the dimensions of the stock GT250 X7 pistons so I can see if I can find a more modern alternative?

P.s. is it a stupid idea to run a single ring piston in an old 2t engine used mainly for street hooning? If so, why?

[husaberg]

Anyone know where I can find the dimensions of the stock GT250 X7 pistons so I can see if I can find a more modern alternative?

P.s. is it a stupid idea to run a single ring piston in an old 2t engine used mainly for street hooning? If so, why?
Yes cause it wears the rings faster, more fun riding than fixing
TKRJ
give me a minute
http://www.tkrj.co.jp/goods/m-AS0800X--11300.php

watch the ring peg location
RG125
http://www.tkrj.co.jp/goods/m-AS0530X--36A06.php

[Grumph]

Anyone know where I can find the dimensions of the stock GT250 X7 pistons so I can see if I can find a more modern alternative?

P.s. is it a stupid idea to run a single ring piston in an old 2t engine used mainly for street hooning? If so, why?

For those of us dealing with the earlier T20/TR250/T250 the X7 piston is the modern alternative....

[husaberg]

For those of us dealing with the earlier T20/TR250/T250 the X7 piston is the modern alternative....

Well if that's the case then RG250 pistons or a few model CR125 pistons will also work then.
http://www.t20suzuki.com/racepic/pistons.jpg
http://www.t20suzuki.com/racing.htm#pistons

[Muciek]

Sorry for thread hijack , I have the 76 rd250 want , to do same thing as Chris ,any mods or tips ? Bike will be ridden occasionally but I don't want to turn it into poor mans tz. I wanted to do cleanup in cylinders , close up the squish into sub 1mm range and do oring mod for the head. Any other ideas?

[husaberg]

Sorry for thread hijack , I have the 76 rd250 want , to do same thing as Chris ,any mods or tips ? Bike will be ridden occasionally but I don't want to turn it into poor mans tz. I wanted to do cleanup in cylinders , close up the squish into sub 1mm range and do oring mod for the head. Any other ideas?

Get some late YZ85 reed valves, put on new reed rubbers they are quite cheap if you go aftermarket, get the squish at the min recommended otherwise its a waste of time.
Keep the airbox.
The other thing I would suggest is use RD350 cylinders as its free torque and HP.

[F5 Dave]

Learn how to measure compression. Squish up to 0.7mm and tgen w
lower compression to suit gas and either 125 or 175cc

[Muciek]

Wanted to keep it 250cc, I don't have the 350 exhausts and elbows since there are not many RD's here. Also I will install CDI iginiton with 2 maps (already have it from other project) should help also.