Suzuki 2 Strokes

Hi all.
My winter project bike is out and about now for a couple of weeks and I've put about 400 miles on her. I've got the cold start issue solved to an acceptable degree, (first or second kick when the temp is above 45F; a few more on the colder mornings) and the bike is running great.
Some of my riding is done on roads with 90kph limits, (55mph) and traffic, (much of it semi trucks) runs on average about 105kph (65mph).
I'm running stock sprockets, (gearing) and I've quickly learned that the gearbox is my friend
Sixth gear is pretty much useless as soon as I'm faced with a head wind or any sort of elevation rise. I'm not complaining, expected the performance I'm getting, but the only other two stroke street bike I've owned was my '76 GT500A. (As everyone here knows, the Titans are quite torquey and pull well from low revs, seldom did I need to gear down or run much over 5000rpm)

What I'd like is some reassurance that what to me, feels like flogging her at 6000-6500rpm for long-ish periods of time, is normal running conditions for these bikes.

Relic

5-7k rpm is quite normal running for those. Back in the day, they used to rev much higher of course!
You're only just in really good torque band there.
If you're wanting to use 6th more, go up a couple of teeth on the rear sprocket, but the downside of that is you'll be using the gears even more.

The Hustler is probably my favorite Suzuki of all time due to the fact that it's the only bike I've owned from new! As to your findings with revs, why do you think they had six gears? I never had any trouble with mine and if a mad 18yr old couldn't kill it I would think it will be safe nowadays.

Thanks for the replies gentlemen. Exactly what I was hoping to hear!

Relic

As said above, above 6K rpm is where the torque and power is and that's where the motor wants to run, so don't be afraid of using it ... just feed her good oil and keep the timing in tune, and she'll be fine

6th gear on the 250 twins and the 380 triples was always an 'overdrive' for cruising, in stock trim and on standard gearing neither bike will fight a headwind or pull up a long incline in 6th.

I am assuming you have a fresh bore or well in spec. Make sure you timing is advanced as Suz says for even a 1-2 degrees retarded you will loose power. Check often for new points loose a 2 couple degrees quickly.

If you want a bit more power widen the exhaust port 2-4 mm and don't change height. That little bit helps some and without changing personality.

But if you want to cruise interstates 65-70 MPH with grades a 250cc can do it, but always pegged running 6000-7500 RPM. Even 10% power gain or loss makes a difference.

nice bike

Update: When running highway the 250 is mostly between 3/4 to full throttle. I have found the GT250 73-75 and T350s 70-72 are a little rich on main jet. You can tell by driving when the bike is comfortable pulling 1/2 to 3/4 throttle. Go full throttle and then back off to 3/4 throttle fast. Does the engine gurgle/4 stroke for a moment when snapped back to 3/4 throttle? If so it may be a little too rich.

If you want to run highway speeds, timed correctly, jetted on main properly, maybe a little wider exhaust port (optional), you will be generating the maximum amount of heat and need to get rid of it. Consider changing to one size cooler plugs. Also look for the T250 Heads with Canted fins (Europe?)... these have more cooling area.

Thanks for all the info. Greatly appreciated.
I'll keep an eye on the timing as I did install new points.
I run Yamalube 2S and it seems I've got it pumping a little rich as I did the math on a measured amount vs fuel consumption over 340 miles and came up with 34:1 (I asked about this on the "oil" thread yesterday) But the plugs look fine, just a shade darker than what I'd call a sandy brown. I think the mains are right as I have done the test you describe a couple of times when I found myself in 5th at WOT. I backed off just a touch and there was no change; backing off a hair more saw the rpm begin to drop.

I'm happy with the performance but with no experience to relate to other than my 500 I was a little uncomfortable wringing her neck.

Thanks Craig380 and Vintageman for the help!

Relic

A little more oil is definitely better for the engine than a little less ... it helps to give a better ring seal and keeps those old bearings well lubed too. Yamalube is a good oil.

As you mention, check the timing every 500 miles or so as it will change with new points, as the fiber heel wears in. A smear of grease on the point cam, and wiping a trace onto the mating surface of the fiber heel with a business card will help reduce the wear.

Back off from full to 3/4 with a quick change. The engine should be loaded, but not overloaded, and say 6500 -7000 rpm.
If you go from 3/4 to full quick and no change in power, back off to 3/4 and if doesn't gurgle, but instead has more power at 3/4 versus WOT too lean

Maybe you did this and all is well. Good you check plugs

Yes the 250 has to work hard to run a highway. I am pretty sure mine was OK in 6th gear cruising 65-70 MPH say only having to deal with road resistance and no additional wind than what it' making.

I am pretty sure I would be near 3/4 throttle to hold that. If I go full it should accelerate a little more but just barely, better to down shift to 5th. Your top end may not be seated yet, timing changed a little (big difference) or a tad rich (lean?) where more throttle is applied: every bit helps.

So if you check all these that what she can do. 250 cc are great for State roads and twisties

relic wrote:I run Yamalube 2S and it seems I've got it pumping a little rich as I did the math on a measured amount vs fuel consumption over 340 miles and came up with 34:1 (

Guessing about 30mpg (I'm working in imperial gallons) that would be about 2.6 pints of oil. Maybe a tad rich oil wise, but other than maybe a bit smoky, it might just knock a bit of performance off, but I wouldn't worry about it.
I use a semi synthetic oil in the GT550 now and it smokes a bit less and runs well with standard pump setting.