An old one but a good one…..
All models T500 from 1968 to 1972 (i.e. Cobra to T500J inclusive) carried 1200cc of transmission oil.
This amount of oil was inadequate to prevent wear on 4th and 5th gear (the case hardening failed).
To overcome this it was necessary to build up the dam wall on the lower crankcase to increase the amount of oil in the transmission. Purely adding oil was of no use as it just overflowed into the clutch case.
Suzuki finally issued a service bulletin advising of the need for extra oil in the transmission case and supplied a rubber part to build up the dam wall. It is best bonded into place. Before this advice, most of us just modified the dam wall ourselves, often out of metal, bonded into place or welded.
The required increase in transmission was 200cc, an increase from 1200cc to 1400cc. The lower transmission cases were modified from 1973 on for the T500K model, but they didn’t change the casting on the top crankcase cover from 1200cc to 1400cc. They relied on a 1400cc sticker over the cast in advice of 1200cc! Of course the sticker soon fell off and many owners only put 1200cc which did no good for the transmission nor the clutch!
For the T500L on (i.e.1974) onward the top cases were changed to read 1400cc.
So in summary if your machine was built from 1968 to 1972 (i.e. Cobra to T500J inclusive) , the engine needs to be split to modify the dam wall to help protect your transmission.
If your machine was built from 1973-77 (i.e. T500K to GT500B) it should have the required modification factory fitted.
Through all of this. the oil sighting screw on the clutch case. was never changed, for the simple reason it still worked as intended. In a 1200cc box, 200cc overflowed the dam into the clutch. In a 1400cc box, 200cc still overflowed in to the clutch housing. The oil levle screw is an easy way to check if your motor has the raised dam or not.
Pic is of a modified oil dam…
ON THE LEVEL…..
One of the difficulties we face is that of the same old problems coming up time and again, and how often one can justify airing them without boring the old hands! One of the favourite questions on the Suzuki side concerns the T500 gearbox, and how much oil it should contain.
In the past I have mentioned that the recommended amount was increased from 1200cc to 1400cc, with stickers on the crankcase covering the old value. Since the level screw in the clutch cover was not adjusted accordingly – and obviously for older models there was no sticker anyway – owners were advised to measure 1400cc of a quality oil in to avoid trouble. I always use EP90.
Some sources reckoned 1600cc was the way to go, without coming up with anything in writing to back it up. However, I’ve just got hold of Service Bulletin M-062 from October ’73 which gives more information on the problem and may help to explain why some people go for 1600cc.
“Transmission oil amount has been increased to 1400ce from the initial production of the ’74 models (T500L), engine number 68083. A rubber flashboard and a sticker printed “1400cc” have been employed as temporary parts until new style crankcases are completed. The flashboard works to raise the oil level of the transmission chamber by 10mm more than the previous level. On new style crankcases, the partition wall height between the transmission chamber and clutch chamber will be increased by 10mm. The new style crankcases will be installed in the T500L assembled from December production.” Crankcase part numbers were identical!
Further – “On the earlier models, for repairs having need of crankcase disassembly, it is highly recommended that the oil level of the transmission chamber is increased by l0mm….as the flashboard is no longer available, it is advisable to build the casing up with weld if the crankcases are split.”
So, as I read it If you have a T500L or later you want 1400cc. If you have an earlier model with a 1400cc sticker, it has been “modded” while the flashboard kit was available, and again you want 1400cc. If it is any early model without a sticker it certainly wants at least 1400cc, but if nobody has been at it with the Lumiweld the level will still be a bit low where it counts.
Putting in 1600cc might give you the correct level in the transmission chamber, but will overfill the clutch chamber! You pays your money and takes your choice…..
DON LEESON