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Post by jon on Oct 4, 2020 10:15:21 GMT 1
Has anyone any experience with matching YPVS crankcase transfer ports with the cylinders?
They seem up to 2mm out in places.
I think the casting is around 4mm think in that area? So removing a little is unlikely to weaken them to failure?
Does it make much difference?
Jon
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Post by Tobyjugs on Oct 4, 2020 10:23:19 GMT 1
Theres no harm in matching them just don't make them bigger unless you have a specific tune as it can be detrimental.
Unless you're going for a special tune i would not bother.
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Post by midlifecrisisrd on Oct 4, 2020 10:32:09 GMT 1
I was told that it is only done when trying to get every possible bit of power out an engine
Mine 385 done but mainly because they were done when I bought them lol
Steve
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Post by jon on Oct 4, 2020 10:54:10 GMT 1
Yes it’s for a tuned 385 engine with all the trimmings.
Jon
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Post by JonW on Oct 4, 2020 11:13:28 GMT 1
I always do it if its way out. Defo do it on a big bore cylinder etc.
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Post by 4l04ever on Oct 4, 2020 11:18:53 GMT 1
My 31K base gaskets are matched to the cylinders, so you can use the gasket as a guide on the cases to see what needs removing.
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Post by jon on Oct 4, 2020 11:22:05 GMT 1
My 31K base gaskets are matched to the cylinders, so you can use the gasket as a guide on the cases to see what needs removing. Hi Rob, Yes I’ve already twigged that yesterday. I must say they are a very good match to the cylinder. I was going to use a scalpel on the OEM ones placed on the cylinder, but yours are more than close enough. Jon |
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Post by Tobyjugs on Oct 4, 2020 11:59:35 GMT 1
I always do it if its way out. Defo do it on a big bore cylinder etc. On my big bore engine they were matched but also filled with epoxy resin. |
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Post by tony2stroke on Oct 4, 2020 12:35:50 GMT 1
As with everything there is more than 1 train of thought on this, my take is that matching all mating surfaces is a good thing, helps reduce turbulence and aids breathing, others say turbulence is a good thing (to a degree) and can aid scavenging, its something I almost always do, I like the whole intake / outlet system to be smooth, I suppose only a back to back dyno test would tell for sure, but even then maybe not, dyno is not the be all and end all, some things work on paper that don't in real life and vice versa.
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Post by reedpete on Oct 4, 2020 12:56:35 GMT 1
You won’t find a factory race bike with steps and rough casting sploges....
But we are not talking about building race engines...
Sometimes the clarity of objective is lost in the general enthusiasm of a project.
So ..
1. What are you trying to achieve, a very specific performance target or just a BBB. (big bore build ) ?
2. Is it brutal , min cost, min barrier to achievement project?
3. Any space for OCD engineering luxury...?
These answers will steer action and priorities...
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Post by rigga on Oct 4, 2020 13:03:04 GMT 1
I think any small improvement, builds up to a bigger gain, so even the smallest gains can be worthwhile in conjunction with others.
Will you notice it or even is it worthwhile on a road bike is questionable, but if you're in there anyway, and it costs little to do aside from some time, then I'd do it.
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Post by jon on Oct 4, 2020 13:28:53 GMT 1
I guess it’s, some of the above.
A bit of OCD, a bit because it should match for performance (however little, I’m not expecting to notice it) and a bit because I can.
Would get me out of doing a bit of plastering I should be doing too LOL.
I was after people’s experience of doing it. Does it weaken the cases etc.
If the cons outweigh the pros I leave alone.
Jon
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Post by headcoats on Oct 4, 2020 13:38:17 GMT 1
On here he is even taking out the rough casting as he is saying it's a problem for flow
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Post by reedpete on Oct 4, 2020 13:53:43 GMT 1
By itself doesn’t weaken the cases significantly and if anything, when accompanied by profiled in fill using chemical metal, makes it stronger.
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Post by tony2stroke on Oct 4, 2020 14:23:53 GMT 1
I have never had any cracks or splits because of doing it, never caused an adverse reaction for me, always been happy to know I done it, after all IMO its how it should be put together, they call it blueprinting, at least that was the 1st I ever heard of it.
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Post by headcoats on Oct 4, 2020 14:28:08 GMT 1
Speaking of blueprinting what would be involved in doing some PV barrels?
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Deleted Member
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Post by Deleted on Oct 4, 2020 15:26:05 GMT 1
Great question Martin, I'll await eagerly to the answers
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Post by headcoats on Oct 4, 2020 15:31:32 GMT 1
Mutts nuts mentioned the powervalves need trimming but is that just flattening the hump on the powervalves flat ?
I have seen some powervalves where the tuner has broke through into the bolt area that clamps the two halves together
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Post by marrcel on Oct 5, 2020 8:54:14 GMT 1
The flow area of the pv is bigger than the exhaust port. To get back to case transfer matching. There is a thread on torque figures. I noticed that my torque specs for a oem bore and stroke pv were a bit higher. I was the onely one who mentioned casetransfer matching. Just a thought 😉  |
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Post by marrcel on Oct 5, 2020 8:54:57 GMT 1
And stock  |
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Post by skydemon on Oct 5, 2020 9:55:11 GMT 1
I think any small improvement, builds up to a bigger gain, so even the smallest gains can be worthwhile in conjunction with others. Will you notice it or even is it worthwhile on a road bike is questionable, but if you're in there anyway, and it costs little to do aside from some time, then I'd do it. The problem is nowadays is we all have too much money. 1 horsepower here 1 there when all we really need is a massive poo and lose some of our middle aged spread and voila 5 hp instantly. We never tinkered so much with them back in the day but I always say if it makes you happy then go for it. 👍🏼👍🏼👍🏼 |
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Post by bare on Oct 6, 2020 18:00:09 GMT 1
Old guys fixate on OCD stuff... It's an Age thing.
Easy... cheaper even, to buy a faster more capable Motorcycle. If that were the actual intent :-)
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Post by skydemon on Oct 6, 2020 19:01:52 GMT 1
Yaaassssss but where the fun in that lol
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Post by Tobyjugs on Oct 6, 2020 19:06:09 GMT 1
Old guys fixate on OCD stuff... It's an Age thing. Easy... cheaper even, to buy a faster more capable Motorcycle. If that were the actual intent :-) It's better to have an old scary, gnarly two stroke beastie that people have only heard fabled stories about, than a super smooth rocket ship. |
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