Cylinder head modifications

Figure out maintenance issues and discuss modifications
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madness
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Cylinder head modifications

Post by madness » Mon Sep 28, 2015 10:11 am

Hi, guys.

That's what we do here right now between drinking vodka... ;)
Main idea is to increase diameter of intake channel from 22mm to 27mm and make it more smooth. i.e. increase the filling of the cylinder (and power) at high revs on malossi BBK, wich is extremly inufficient with stock head, "factory calculated" for 150cc.
In stock, 150cc had 12 000 revs, and 170cc, with best carb, i could get, had only 9 500 - 10 000 revs. With help of very easy calculation, volume of air-fuel mixture, pumped through 150cc at 12 000 revs seems pretty equals to that volume for 170cc at ~9-10 000 revs. So, 170cc cylinder just can't breath enough with this head.
So, i've decided to modify stock head...
The goal is to reach the highest possible speed.
All other modifications are around of this, to make it complete.

If you have questions - ask.

P.S. Road tests will be done soon.
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waspmike
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Re: Cylinder head modifications

Post by waspmike » Tue Sep 29, 2015 1:57 am

Looks good, lots of work.

I did a Wave 100 cylinder head once as a hobby whilst working in the jungles of Indonesia.

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madness
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Re: Cylinder head modifications

Post by madness » Tue Sep 29, 2015 5:41 am

Thank's!

And what has changed (in riding) after modifications were made?
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Re: Cylinder head modifications

Post by waspmike » Tue Sep 29, 2015 7:40 am

I didn't do any comparison testing as it was a hobby in a remote place done for sanity so the process was more important than the results. I did by a digital tach but the fist time I put it on and went for a ride the display climbed up to 9999 then flashed and it never worked again. :lol: Later I got an analogue tach. Sorry no engine pictures i didn't think to take any.

Image

I only did the ports. I didn't get larger valves until by some luck I managed to find a big valve head.
My motor also had a "race" cam, larger carburetor, free flow exhaust and cylinder enlarged by about 20% volume.
Top speed indicated 115 and it would easily keep up with a Suzuki Crystal 110 two stroke which has 12.5hp against the 7.2 that I started with. I did that one day coming back 75kms from town "racing " with a local from the same site. Oh and an oil cooler as it was air cooled.

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madness
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Re: Cylinder head modifications

Post by madness » Tue Sep 29, 2015 10:05 am

Well, all i do, is preparation for riding looooong distances. Thousends of kms... Nearest real sea (Black Sea) is about 500km from me. And sweetest parts of Krimea is about 1000km.... Northern White Sea, i want to visit next year, is 3000km from me.
Have no overheat problems, becaurse there is 2 radiators in my scooter. Now it's autumn, no heat, but for hot (+ 35-40C) summer, i have manually switched electric coolant-pump and manual switch for radiator's fan.
And i'm going to make most powerful engine from SH/Outlook/Outlander, call it "sport" or "racing", no matter...
One thing make me sad - i can't use Yuminashi parts for my scooter... :( They are the best.

P.S. electric coolant pump is very useful in case, when engine, running long time on high revs and heating much, goes down to low or idle revs, on wich productivity of mechanical coolant pump depends. coolant flow slowes down and local overheats happen. you maybe have seen, when you stop after long ride, temperature, been normal before, began to rise quickly ;)

P.P.S waspmike: we have such slogan here, for racers etc... "Hone a Head, be a Man!" Respect! 7.2 -> 12.5hp is about +70% ;))) wish i could do this...
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Re: Cylinder head modifications

Post by waspmike » Tue Sep 29, 2015 10:22 pm

I am not sure i got anywhere near 12.5 :o but... if it is possible from a two-stroke then...
Mine wasn't built for reliability so if it had broken then i would have simply started again.

I am not sure you can use Yuminashi on the newer version either as I asked once about their gear up kit and their ratio quoted does not match anything for an SH150, it was actually lower not higher. :idea: So for gear up we only have Malossi primary or Polini secondary. Or the other way around :?

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Re: Cylinder head modifications

Post by madness » Wed Sep 30, 2015 1:34 pm

HPs are just numbers, competition is the only way to find out real value of scooter's "effective power".

About Yuminash's parts...
They didn't discover anything new. All, they do, can be made right here, in my city. Heads increased diameter for BBK, with intake valve 31mm, for example. Lightened valves. Even custom camshafts. And matherials! Mmmmm..... I mean, any kind of steel, titanium, all alloys, used in heavy industry upto space, they all are pretty easy to get here, in Russia. Prefered in tons, but.... ;)
Another example: all our racers prefer hammered pistons, not casted. So, here are some places, where that matherials can be prosseced profesionally. Ka-50 and Mi-28 been produced in my city too ;)

Gears installed are Malossi AND Poliny. Both.
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Re: Cylinder head modifications

Post by robber57 » Fri Dec 11, 2015 2:10 pm

You did a nice job but apparently nobody told you to leave the valve guides alone and NOT to shorten them, the guides are about the only place where youre valves get cooled, you severely shortened this cooling which will probably lead to valve overheating not to mention that there is little left to actually guide the valve and provide sealing.
on the exhaust its even worse, there is more valve stem exposed to hot exhaust gas so it will get hotter AND there is less guidance so less cooling which will make it even hotter.
the "upside" of having a bit less friction (because the valve is still there in the inlet opening) to the mixture is not worth the trouble. or at least thats the general accepted idea, you shorten the lifespan of the valve train to a very low mileage.

I wonder if you gave this whole tuning idea enough thought....
Failure is not an option, it comes bundled with the package.

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Re: Cylinder head modifications

Post by madness » Fri Dec 18, 2015 1:04 am

Such "cutting off" valve guides is acceptable. I know, of course, all the consequences of this, and it's OK for me, as i have prepared another pair of valves and guides, when decided to cut so much ;)
Idea was to maximize air flow by any costs :) Local mechanican, who prepared thousands car engines for race, told me, that valve guides are pretty long in my case and cutting them so, is not deadly.
About mileage... right after this modification i had a little travel (>1000km) almost all the way at max revs. Here is a story (including results in valves): viewtopic.php?f=5&t=6213

Btw, one more modification made to make intake more smooth and to reduce the turbulence in it.
And the engine now "sings" at high revs.
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Re: Cylinder head modifications

Post by robber57 » Fri Dec 18, 2015 3:16 pm

Did you also increase injection manifold size? (where the butterfly valve is)
if it is still @ 26 mm you can tune all the world but it will go hardly any faster, its the smallest hole in the chain that determines how much mixture can go through....
Did you do any fuel managment?

What you really need to do is:
big carburettor (or a fully programable injection with bigbore housing)
K&N or DNA airfilter
an unlimmited ignition that will go on strait to 12500 rpm
better valve springs
Weight reduction on valve train-crankshaft-piston and rod

This thing is just not made for over 10.000 rpm adn if you try you will pay a high price learning what will break and what not.
Keep in mind this SCOOTER has a "assembled" crankshaft so not made from 1 block of steel but build from more parts, if you overdo it you may pick it up from the road after the connection rod opened your crankcase and the whole thing fell on the street....
perhaps lower compression, keep in mind its only two valves and not a hyper 4-valve CBR-RR, you need to use old school tuning
Failure is not an option, it comes bundled with the package.

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