Suzuki 2 Strokes

Have you every seen this bulletin?

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... ink:top:en" onclick="window.open(this.href);return false;

Pretty cool. 60-65 HP at 7800

Nothing I am going to do.

The person copies enough pages on post you can read it.

Should be posted for free somewhere if not all ready

Another here.
http://www.ebay.com/itm/1969-Suzuki-T50 ... 9948766%26" onclick="window.open(this.href);return false;

If you avent seen this , here is a listing of service bulletins http://www.oldjapanesebikes.com/mraxl_G ... etins.html" onclick="window.open(this.href);return false;

I did not see that at the oldjapensesbike or Ozebook.
Makes me think Suzuki had more such bulletins. So did the others Jap manufactures

The one on the eBay post had all pages displayed I think. I did save the images. I feel so cheap for not buying it. If I would have used it maybe I would have (nah). I should at minimum thank him for posting it.
So far I read it once briefly and a few things I found interesting if I understand and recall correctly next.
They want you to mix oil with the gas 40:1 in addition to the oil pump (that’s nothing new) and talk about another arm for the pump? I think it makes less oil injected to compensate for the oil added via tank. I still think the total oil is more (seen other example where it is), not sure, maybe not. Here is what is shocking to me. It says for a couple more horsepower turn off the pump (oil contribution?). The footnote says, this can affect crank life, but if the last lap of the race who cares if you have a chance at ending up front.

It doesn’t give you a dyno plot but, says the new power peak is 60-65 hp @ around 7500 or 7800 if I recall. But then it says if you go above 8200 piston skirt will break. Wow! that is close to peak. I heard rumor the piston was the weakness and now I see it directly from its creator.

I am not sure when or if a forged piston was around back then. But today we have Wossner making them. Not cheap (but, not too much more than OEM I bought for mine either). If you want to rev above 8000 rpm good insurance if the skirts are indeed made stronger.

Also I find the porting just one spot/side per port. Just lift top of exhaust port roof and lower intake floor. Check for good match and specifically one side of transfer (angle side with casting?) No widening of anything so should be easy on rings and much easier to do. The T500 has the canted ports but exhaust still exits out front as we know. It is tough to blend any widening all the way through due to bend it makes to exit exhaust.

5mm change both side may be quite for street rider?

For 5 mm off exhaust it says to shave only 1.5mm from head. It does not say If the compression is restored back to stock, I would think goal would be a little higher that stock, but domed head so maybe not too much more else pre-detonation. No reshaping of dome is required.

I always wonder how much to shave head if I raised port. For example If I raise port 1mm and the engine runs slow I think I need to take 1 mm of top of barrel for example to be the same real compression. If running at 8000 rpm I wonder if most all gas still has time to escape out the exhaust window or only 50% for example… I still think most does??.

If not RPM dependent and all is lost out window then simply use the volume of cylinder to see how many cc were lost. Then if you want to get it back via the head only take off same amount of cc. This is a little more geometry/math if you have to get into the dome. Suppose you could use a syringe and measure the change in head ccs as you mill to verify the math.

Lastly the expansion chamber design looks a lot like my jemcos for theT500. My bike is in storage, but when I get it out I’ll measure. John at jemco did say to me some of his designs back in the day were actually from Suzuki, how many which ones I did not ask.

Mike S

Thre are two ways that people calculate Compression ratio and both are inaccurate when a motor is running. 4 Strokes typically use 'Static" CR which is (Clearance volume + swept volume) / Clearance volume and yields numbers typically around 10:1

On 2 strokes, someone stated the trend of using "corrected" which is similar to the formula above but only includes swept volume after the exhaust port closes.

Both have problems. The Static assumes that all the gas in the cylinder is compressed which ignores the fact that the valves are not closed at BDC. The Corrected calculation assumes that no gas is trapped until the port closes which is equally inaccurate.

In both cases, the formula is fine but they ignore the effect of wave tuning. On a 2 stroke at low revs, lots of gas escapes from the exhaust port. As revs rise, more gets trapped and at high revs when the exhaust pipe is sending back stuffing waves, compression may actually be higher that static.

So with a T500 race bike, raising the exhaust port will reduce the effective compression ratio at low to mid engine speeds and may be the same or even higher at high speeds when the pipe starts to work. That's one reason why raising the exhaust port hurts low speed torque. The same applies in the inlet port. At low speeds, more gas gets shoved back out the port on a low port floor and that hurts the bottom end.

All of those things are time and wave dependent and to see the effects a program like MOTA is most useful. It calculates cylinder pressures and wave patterns and you can see the effect of changing any of the variables.

So to recap, raising the exhaust port does reduce effective compression in the lower half of the rev range and a big enough change without a matching pipe change will hurt power all the way up. How far can compression and porting go? That depends on a number of things including cylinder head geometry. On a street T500 do everything in moderation.

Vintageman wrote: Lastly the expansion chamber design looks a lot like my jemcos for theT500. My bike is in storage, but when I get it out I’ll measure. John at jemco did say to me some of his designs back in the day were actually from Suzuki, how many which ones I did not ask.

Mike S

A few JEMCo pipes are copies of Suzuki Perfomance Bulletin pipes and in the case of the T20/250 they are an awful design for the street. I spend days trying to work out how to make those pipes work on a street motor and there's no simple answer. Some of his other pipes are really good.

Do not use an old school pipe on a street motor. Not nice. There are much better designs around that those. Late model TR750 pipes are pretty good on a race bike though even today.

Vintageman wrote:I did not see that at the oldjapensesbike or Ozebook.
Makes me think Suzuki had more such bulletins. So did the others Jap manufactures

The one on the eBay post had all pages displayed I think. I did save the images. I feel so cheap for not buying it. If I would have used it maybe I would have (nah). I should at minimum thank him for posting it.

I haven't put that one up on my site - first time I'd seen it. As you say, there seem to be more and more of this stuff coming out of the wood work with the passage of time.

I'm sure I have a copy of this article somewhere....that I have had for 30 years plus.

titan performance wrote:I'm sure I have a copy of this article somewhere....that I have had for 30 years plus.

If you email me some scans, I'll add it to the bulletins page (at this link).

oldjapanesebikes,

Sent the email