Pre '73 T500 1200-1400cc transmission case modifictation

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mafd2
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Pre '73 T500 1200-1400cc transmission case modifictation

Post by mafd2 »

I've read and heard conflicting stories on the 1200 to1400cc conversion on the pre '73 tranny case. So, does the transmission have to have the 1400cc oil wall modification? I've read articles where 4th/5th gears were starved of oil damaging the gears. I've read articles where people have gotten thousands of miles with no problems and this problem has mostly occurred back in the early 70's when there were only a few oils to choose from (and not the best quality) where there was extreme heat on long runs but, this didn't happen to all the transmissions. One mechanic said with todays synthetic oils, and metal treatments like Z Max, ZX1, Cermatreatment designed for motorcycles and wet clutches the mod wouldn't be needed. So then, does the 4th/5th gear get only a small amount of oil but just not enough? Has anyone had the problem recently or was this something that occurred in the 70's? Opinions? Thanks.
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by Coyote »

So then, does the 4th/5th gear get only a small amount of oil but just not enough?

That's the way I have always ubderstood it. If it were mine, I would do it just because. Better safe than sorry. I have seen pics of some really fried gears. On the flip side, there must be hundreds of early T500's running around that never had that 'upgrade' and still work fine. Probably more than that went to the graveyard because their transmissions were shot.
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mafd2
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by mafd2 »

Thanks for the input. I guess I'm wondering if anyone has heard of or had this problem recently without the modification or was this something that happened 40+ years ago.
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by argo1974 »

These days T500 owners are too concentrated on transmission oil level modification using oil dam piece with additional 10mm height. On pre-74 bikes, 4th and 5th gear teeth are submersed into oil bath around 10mm which is sufficient enough. In engineering, this is a function of tooth module (near 2 on these particular gears), usually 4x or 5x tooth module is used for submersion level. In T500 engine, two different oil levels are maintained, higher level for transmission case and lower level for clutch case. The latter is used to reduce clutch drag, which will decrease power loss in primary drivetrain around 3 to 5%. Sadly oil overflow and/or leakage from transmission case into clutch case is not restricted enough, whereas oil collecting from clutch case with oil receiver plate isn't sufficient enough to compensate. Over the years, different solutions have been used to solve oil shortage problem in transmission case. E. g., using re-designed oil receiver plate or using the same oil level in both cases. The latter idea will work in two different ways, just filling in oil until both oil levels equalize around 15mm below engine case horizontal dividing line. Additionally, another 10mm hole could be bored vertically from main oil drain plug hole (engine case wall thickness is around 5mm there) to short circuit both the transmission case and clutch case.
There are lots of later transmissions around with damaged gears which is showing clearly, that oil dam + 1400cc oil won't work well. In my T500K, I've been using oil dam + 2L of transmission oil with excellent results.
1x T500 Cobra (1968)
4x T500K (1973)
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by mafd2 »

Thanks Argo for the info. Not sure I follow you on how to know when the oil is equalized. Aprox. how much oil is used to equalize compared to the 1200cc going 15mm below the horizontal line? How high would that put the oil up the clutch basket? Also don't quite follow you on boring a hole. Are you saying go in straight through the oil drain hole and bore a hole in the case? What does this do? Does this have to be done to equalize the oil? I'm just trying to picture things. Thanks
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by argo1974 »

Oil dam height on pre-74 bikes is around 20mm below the mating surfaces of the engine case. While filling in oil, get the bike on center stand, and connect transparent tube via M6 banjo bolt to clutch cover: http://oldjapanesebikes.com/1968_T500/i ... _4413a.JPG" onclick="window.open(this.href);return false;
Oil starts to fill clutch case after overflowing the dam in transmission case, so fill in until oil level in the tube reach 15mm below horizontal line of the engine case. Note the amount of oil filled in (approx. 2L). Make yourself a simple dipstick, e.g. us a nail or piece of wire in oil filler plug. In the future, for measuring oil level in transmission case, use that dipstick, and in clutch case, the transparent tube. This is quite a mess since you will have to lean the bike to left side for connecting transparent tube to clutch cover.
As mentioned earlier, you could connect both transmission case and clutch case directly by boring an additional hole. Then you could measure oil level using the dipstick only since oil levels are always equalized (oil dam is useless). Once clutch case oil drain plug (the one sitting lowest) is removed, you can feel another wall behind that hole. Should be around 30mm from gasket surface into the hole. Use 10mm drill bit and bore straight into the oil drain hole until you break into transmission case. You will go through the hump on transmission floor seen here: http://www.oldjapanesebikes.com/1968_T5 ... _4086a.JPG" onclick="window.open(this.href);return false;
Make sure you won't damage thread windings in oil drain hole. E. g. I use shortened drill bit with effective drilling length of 15mm for that job.
On other two strokes of the same era, equal oil levels are pretty common, e.g. in my 69" Kawasaki H1.
1x T500 Cobra (1968)
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by mafd2 »

Ok now I'm getting a better understanding thank you. After the hole is drilled do you now use the 1200cc of oil?
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by argo1974 »

Nope, oil amount is around 2L (15mm below horizontal line).
1x T500 Cobra (1968)
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by mafd2 »

Great thanks!
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by Pete O'Dell »

sorry argo I have to totally disagree with you 2l oil with give you clutch drag, I modify all 1200 cc engines to 1400, we run our race engines at 1400, the only later engines you will find with gear damage are where owners have used the oil level plug instead of measured amount.
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by argo1974 »

Pete,
I have been riding my restored T500 with 1.8L to 2L of oil inside the gearbox for 3 seasons (around 7000 miles) with absolutely no issues. And, I'm pretty sure, clutch submersion level into oil bath has no effect to clutch slippage. But yes, the higher oil level in clutch case, the more energy is lost due to oil drag, up to 5%. That might sound a lot in racing.
And, I have 20 more two stroke bikes (350cc to 500cc) in my garage with engines maintaining equal oil levels in trans and clutch case. E. g., my 1969 Kawasaki H1 500 with more HP and torque, while having smaller clutch than T500, runs just fine with 1.6L trans oil. Due to narrower gearbox, it has smaller volume transmission case though.
Back then, Suzuki had to update transmission oil levels in almost all two strokes they had on the market. Crappy engineering. And, over the last 25 years, motorcycle manufactures provided lots of updated parts to cure their ill-fated bikes, but just little updates, without any real re-engineering. 1400cc oil might work (I've seen far too many damaged post-73" transmissions to believe into it), but equalizing oil levels in clutch and trans case will work 101%. I have good usable T500 transmission on the shelf with 60.000 miles on it, coming out of an engine with equalized oil level mod, the previous owner, a Finnish guy, made at mid 1970-ties.

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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by phabbo11 »

hi guys,just wondering what tranny oil you use?
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by mafd2 »

phabbo11 wrote:hi guys,just wondering what tranny oil you use?
I'm going to start using Lucas 80/85w synthetic transmission oil for motorcycles.

From Argo:
Motorcycle oil of JASO MA1 or MA2 rating is good but 75w80 or 80w90 or 75w140 gear oil of API GL4 (or GL5) rating would be better choice.

In US, e. g. you can go with Belray Gear Saver 80W or 80w85: http://www.belray.com/bel-ray-engine-oi ... -explained" onclick="window.open(this.href);return false;

I use Castrol MTX 75W140 in my T500K these days but 75W140 oils CAN cause clutch slippage. Those oils are the best ones available for lubricating transmission gears though.
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by alfiemorris »

An old post to tag onto here but I use a 20W/50 Mineral oil either that or a 10W/40.. I'll order a dam ready to modify my tranny.
Some people say I'm a complete fool. Ah! But some parts are missing.
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Re: Pre '73 T500 1200-1400cc transmission case modifictation

Post by tintruder »

These guys produce a rubber dam for the 1200cc cases.
http://www.claussstudios.com/id47.html" onclick="window.open(this.href);return false;

I have had good luck using the 75w-140 differential lube from Motorcraft. It has a high sulfur content, which is a great wear reducer. This may be too viscous for racing or use in cold climates, but it also sticks to the gears very well, so they don't go dry if oil is low for some reason.
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