YPVS tune...too much?

[mark350lc]

Just on with a YPVS build at mo. Got talking to one of my customers recently. He is very well known in off road tuning and is very good with 2 stroke porting. He has offered to do the engine for me. He said do I want a mild tune or lots of power? Has anyone here gone too far with ypvs tuning or do the power valves tend to soften the curve to make it still useable on the road?

[headcoats]

I have some barrels where the inlets ate opened right up and caused excessive wear in that area, so my advice would be to have a mild tune.
Depends on exhausts too

[midlifecrisisrd]

As above don't narrow the inlet bridge in the liner

Exhaust port wise most "modern" tuners will leave the exhaust port height alone

Steve

[mouse]

I have a couple of tuned (in the classic sense, ported etc. by well known tuners) YPVS hybrids and they are great on the road.

Both make mid 60srwhp with the addition of pipes, standard carbs, one runs without an air box and one with, both are perfectly usable.

The pre YPVS engines are more peaky in my experience

Mouse

[jon]

To make a 2 stroke engine produce as much power as possible is at the detriment to a road bike.

My advice is tune it for bottom end.

Jon

[dougw]

Many years ago I got to have a ride on the road on Terry Shepherds 350YPS that he developed his "Full Production Race" tune on.

It was lovely on the road , perfect carburation, just felt like more power everywhere, compared to my Terry Becket "Road Tuned" 4L0.

So as long as the tuner knows what he is doing I`d be more concerned about how quickly its going to wear out than rideability.

My stroked and Mutts ported YPVS should apparently go 5000 miles in between top end rebuilds, when it ever gets completed .

[muttsnuts]

Feb 14, 2024 17:50:11 GMT 1 dougw said:

My stroked and Mutts ported YPVS should apparently go 5000 miles in between top end rebuilds, when it ever gets completed .

got several that have done over 8000 miles now and still going strong

[muttsnuts]

back to the point of the post, as most have said, you want it tuning for reliability really, its ok making it do big power but the bores (especially on YPVS barrels) wear very quickly around the transfer port area as there is very little metal to start with, as most have said, try and leave the inlet bridge alone as otherwise it accelerates the wear in the middle of the barrel

The exhaust port is already pretty good on the YPVS, so that can be left to a large degree (widening it a little at the top half helps), a good clean up of the rough casting in all of the ports also helps, as does aligning the power valves perfectly, that alone can be worth 5bhp if they are out of whack (which most are)

HTH

[mark350lc]

Thanks for that, never thought about the reliability side for some reason....just big numbers. I'll tell him not to get too carried away. He does now mainly tune mx bikes for racing but has a history of tuning and racing banshees.

[veg]

Tbh before I undertook any tuning I’d make sure everything else is set right. Dave talks about the pv’s being set right, then I’d check ignition, what do you use? Make sure your carbs are properly set up and clean, what pipes do you have? Going to use? Also be mindful of the chassis, it’s no good having a motor pumping out horse power if the chassis/brakes can’t handle it etc etc

[steve63]

I had a YPVS 31K that had a Stan Stephens Production tune on from new in 83. Raced in 83, 84, 85 and early 86. I used it to take me and the Mrs camping in Spain in 86 and then used it for everything including commuting to work year round for a couple more years after that. Brilliant engine with more power everywhere and not in the least peaky. It still had the original pistons in it when I sold it. I know they were original because Stan opened the holes up in the back of them in his 83 proddy tune. It finished its life in the side of a car I was told. Most of Stans work seemed to be on the inlet ports and the head profile and skimming.

[abar121]

My TZR250 1KT with a full Stan Stephens proddie tune was also super tractable with stacks of power everywhere compared to stock.

But it ate rings for breakfast and needed to be stripped a couple of times per season. It made my road VJ22 RGV seem totally gutless.

I have a mild road tune by Mick Abbey on my 31K running PWKs and it's just lovely.

[steve63]

I don't honestly remember ever changing the rings on the power valve. I even used the same plugs that were in it for racing when I went to Spain on it in 86 and when I was using it for daily commuting. It went onto one pot once but all it was was accumulation of general road crud on the plug. I could see it tracking down the plug to earth. A gave the outside of the plug a good clean and it was back to normal again. The thing was I had been using B10EVs. I've since heard people moan about the EVs but I couldn't see one of the HS plugs lasting like they did for everything from racing to riding to work in the snow.

[steve63]

Feb 16, 2024 14:06:22 GMT 1 abar121 said:

My TZR250 1KT with a full Stan Stephens proddie tune was also super tractable with stacks of power everywhere compared to stock.

But it ate rings for breakfast and needed to be stripped a couple of times per season. It made my road VJ22 RGV seem totally gutless.

I have a mild road tune by Mick Abbey on my 31K running PWKs and it's just lovely.

To be honest it's been a long while since I rode an LC so can't do any proper back to back comparisons with my RGV VJ21. I suppose just going by the numbers it would be pretty flat as there's not much happening below 8,000. On the other hand, on the track at least, It only gets ridden between 8,500 and 11,500 unless I make a mistake and let.it drop too far. I've not been far on the road with it but it is quite happy doing 4/5/6,000 just not very spectacular at those speeds. The Dyno guy was puzzled. He didn't think the power valves were working properly. He asked if It had any! There was a 15hp dip around 8 and a peak of 50.7. All std apart from some home made cans.It doesn't stop like a TZ350 below 8,000 thankfully.