2 Strokes Down Under

Have you recently changed supplier? Its well known that there are a lot of fake sparkplugs about.

As I have said before, I don't confess to know all the worm drive arrangements on the early bikes, suffice to say it would surprise me greatly if the ds7 and r5 worm were the same. You can't run the 21T gear on the ds7 as the primary gears are different between the two bikes.

The wormshaft seal is still available from Yamaha. Wise to replace the kickstart seal too. Good luck with the wormshaft. I will look out for one if you want?

The worm is retained by a nut on that model. You need to take off the r/h case to remove it. A new seal for the worm shaft will also be required.

bosslock wrote:The r5 Pump and ds7 Pump seem identical. Perhaps the worm has a smaller thread thus spinning the cogs on the pump to get a higher ratio of oil?

I have already said this - a few times! Impossible to id that worm from your photo, sorry.

Is there the possibility that the 250 head has been modified at some time in it's life?

I found a cheap r5 pump. I will see how it installs. Would it be the same as my ds7? Cause technically the 350 won't need more oil. It could be a 50cc and still have the same ratio? I have no clue. It won't fit! The gear inside the pump is different. You need the r5 worm drive to go with the r5 pump.

The Yamaha specs for the twin cylinder bikes are; 0.5~0.6 cc on minimum stroke and 5.1~5.7 cc on maximum stroke. This is for 200 strokes. I tested many early build pumps and conducted my own work to find out what made the output less. There are nine different things which affect this. If you have to...

Its the same for all models, per 200 strokes, but like I said strokes per minute for different bikes vary greatly. Its the speed at which each pump is driven that gives you the difference. The only difference between a 250lc and a 350lc pump is the gear inside. The 350 pump delivers 30% extra in a g...

Pump output is measured in what comes out per 200 strokes which makes all the twin outlet ones all the same! How quickly it does 200 strokes is due to many different gear and worm combinations, and white plastic drive gears/primaries.

Just to add, Yamaha changed the gear inside the 350 a/c pump during the production run, so two different pumps.

I am more (totally) confident with the later a/c and lc/ypvs/tzr pumps. I would need to see all the parts in front of me to say for sure.
Arrow.

Hi, its possible to use the worm and pump from the 350. The parts come up on eBay. 250 to 350 oiling is around a 30% increase.
Arrow.

No worries Jon, the wifi is playing up in here so did not edit the post correctly will look in again tomorrow.

Hi happyrd, welcome to the forum. The issue is caused by the clear pipes. They are not made from the same material as the original pipe which is still available from Yamaha. Running at the back of the cylinders the pipes get pretty hot in use and very soft! As they are under constant vacuum when the...