Premix?

[powellm976]

Hi, what's the go with ypvs and premix? I also have an Rgv and the go with them seems to be to leave the premix system going, I've just bought a yammagamma with no oil pump so is that normal? What ratio do I run

cheers

matt

[muttsnuts]

I tend to run 32:1 for LC's etc, but YPVS run much leaner, exactly how much leaner I am not sure, possibly 40:1, but somebody will be along in due course to advise who knows better than me in respect of YPVS's

HTH

[jessy03]

I run my YPVS on 40:1 with no problems.
jess

[powellm976]

Thanks guys

[higgsy]

33-1 is the leanest I'd run the oil, the YPVS race bikes run on 25-1. A decent fully synthetic oil designed for pre-mix is a must

[bare]

My pore Street only Bike has been on ~24:1 Motul.. for years.
Sans any notable carboning and No plug foulings.. ever.
Actually it's pistons / domes have been pretty darned clean whenever I've opened the thing up.
Albeit it is a bit smoky accelerating hard down the road.
Good for filling up convertibles with noxious Smoke clouds.. if that behaviour appeals.
It's Only 'too much' oil when ones' plugs foul.

[powellm976]

Decisions decisions. It is a race bike so maybe I'll start a bit heavier and see how it goes.

[Mad Biker]

i'd go for 25:1 if you are going to be racing it

[muttsnuts]

if your racing it then yes I'd be doing the 25:1 mix as its not like you'll be tootling along !

[powellm976]

Cheers guys

[higgsy]

It did make me think though how come it never blew up before

I guess it depends on how hard he'd been ragging it, pootling along and no flat out blasts and it would be fine, maybe it blew when he finally opened it up!

It's not just the ratio that is important for racing, you need to consider how the oil burns in the combustion chamber, today's fuels are very variable with loads of additives and you should use 97 and above RON in a race bike. Adding more oil helps the ring seal, friction causes heat and power loss so the more oil there is the less friction. It's a bad myth that having more petrol and little oil gives more power, good racing two stroke oils help the combustion process not harm it.

A friend of mine did some dyno testing with different oils for the Aprilia 125's, some certainly gave more power and a cleaner curve. There are a couple of articles on the net, one by racing journo Kevin Cameron, that are well worth a read, he got down to 18-1 with no adverse effects. Bit smokey on the pilots i would have thought!

[anyoldiron]

Theres a lot more to oil in a 2 stroke than just the lube factor, it also helps to seal and create compression, there have been many studies done on this. The optimum for big bores is 20:1, i will see if i can dig out some of the articles, but the difference in power produced by the same engine running 20:1 and 50:1 is significant.

[looey]

Didn't someone on here post a ratio chart some time ago for the oil pumps as designed by Mr Yamaha ?.

There was a massive difference between the ratios at idle and maximum revs on wide open throttle. It was something rediculous like 75:1 at idle and 16:1 at max revs with full throttle.

If your racing and hence full throttle most of the time then premix is perfect, but on the road, the majority of the time you will either have too much or too little oil going in !.

[arrow]

Sept 8, 2014 8:34:19 GMT 1 looey said:

Didn't someone on here post a ratio chart some time ago for the oil pumps as designed by Mr Yamaha ?.

There was a massive difference between the ratios at idle and maximum revs on wide open throttle. It was something rediculous like 75:1 at idle and 16:1 at max revs with full throttle.

If your racing and hence full throttle most of the time then premix is perfect, but on the road, the majority of the time you will either have too much or too little oil going in !.

It was me matey, in the advice section. A few pages back by now.

[looey]

So it was, I found it

rdlccrazy.proboards.com/thread/20427/oil-pump-graph

So basically, if you're running premix and at full throttle, if you're running 30:1, you'll only have 2/3rds of the oil going in that Mr Yamaha intended and at 40:1 only 1/2

Not a problem if you ride around like Miss Daisey though

[steve h]

We used to run 35-1 on 250LCs and 250Gammas for proddy racing, no issues. (Silkolene Comp2) then latterly a cheaper semi synth from rock oil, again with no probs (or smoke)