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Discussion Starter · #1 ·
Ok everyone I bought a used set off PS and ran a thread there without much luck. So here's the deal.

They are stock stroke 68MM bore cylinders and I'm in the process of porting them to raise the tranfer ports and make the extra exhaust ports a little bigger. My question to everyone is what else should I do to these and what gain will it get me. I have done a few cylinders and I know there are "secrets" about things but I just want some input and help on making these better.

From the get go the exhaust is 196 and the transfers were 110. I raised the transfer to 126 or 124 I can't remember right now, but thats about all I could get from them cause the extra exhaust ports are too low to raise the tranfers anymore.

The intake area had a big bridge across the top so I cleaned that up and I'm really toying the idea to add the extra intake ports to them. I see every aftermarket cylinder has them and if I did I would make them as big as I could cause small ports won't do anything for me.

I will post pictures of everything and I got some good ones but they were hard to take. Camatv asked the about the transfer port roof angles and the ones by the exhaust are flat and the ones by the intake have a slight angle up on them. I'm leaving the transfer area alone to see if I can make a set of torquey cylinders out of the them.

I have some questions about the bottom of the cylinder and when I get the pictures up tonight I will show you what they have done. I'm shooting for having them on the dyno next week.

Anyone build a set yet? Anyone even interested? I know there are a lot of things to consider when porting cylinders but you have to look at each thing to get where you are going......that's what I want to get out of here.

So is everyone in?
 

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Sounds like you are off to a good start.

I would skip adding the Boyesen ports- the transfer tunnel volume is too small IMO to go adding flow entrance/curtain issues. There are some motors out there that have issues with low-end tuning never being right regardless what they try with the carbs- but once they put a big fat reed spacer on it- the tuning can be managed. That reed spacer gets the reeds and/or carbs far enough away from the flow reversion aimed directly back from those Boyesen ports. In the general tense of Banshee stock/stockish cylinders- the intake is the last problem to work with. The intake area is quite sufficient.. You can make intake sized you can fit your fist thru it, however doesnt matter much as it still has to go thru the transfer ports.
 

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I know very little about shee's... and to be honest, this might be the first post I have read about porting the Vito's stuff.... Might be why not much info is out there.
 

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Discussion Starter · #4 ·
Dan have you seen a set of these new cylinders yet?

There like having a set that's been welded inbetween the transfers and the transfer divider is pretty small or thin. You would have to weld the stockers to make it like these. The 2 extra exhaust holes are pretty small. I remember a builder tell me once that when he does them there not the size of a pencil which kinda is what these are and you can't make them much bigger cause theres not much meat added there when they cast them.

are the pictures tantalizing anyone yet?
 

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i dont think theres a whole lot of secrets. info published 20 years ago still aplies today. about every cylinder design imaginable has been done over the years at one point or another by different bike/atv manufacturers. theres alot of good books that can help you in your quest
 

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QUOTE (vwpartsman @ Jan 12 2009, 07:14 PM) index.php?act=findpost&pid=25286Exhaust

Wanna see more lets hear it


IMO there seems to be plenty of exhaust area. Those sub-exhaust ports arent that small from what I can see. I would work the liner bottom on the exhaust side to open the transfer tunnel feed. Other than that I dont think I would do any more than what you have already. Also it looks like it could have been run a little hard when it was cold, from the markings on the exhaust sides.
 

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Discussion Starter · #10 ·
Both of the pictures above are stock.

That's it for input? These cylinders are ported and ready to go on the dyno. I thought I would throw out there a new cylinder and get some input on what would work or maybe this would be better but 2 different forums and not much response. Is it me?

Well thanks for eveyone who did respond I thought it would make for a good forum discussion....I really thought this would peak more interest.
 

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I would say one thing to consider is using an extra thick base (like a .040) gasket to get your transfers up another .020 if you wanted into the 128-130 range. an extra .020 will change the transfers about 4 degrees but the exhaust only 2 degrees on a 54 stroke 110 rod motor which would make the exh about 198 degrees. If you were wanting to drag that might be better. The angles of the trans port roofs, and the shape of the roof of the exh port suggest that would be a somewhat broad power motor. May not have much torque being a 54 stroke.
You have a few replies from some guys that know their stuff when it comes to building, tuning. Backcountry and Bubba definately do. I'm somewhat surprised at the shape of the exh port roof it's very high in the middle. Too bad it isnt slightly lower too 2 degrees or so. Let us know how it works for you. Radar
 

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when the port is wide like that the roof needs to be toped like that so it will ease the rings back into place. i think the ports a lil wide with the triples it could be a lil wider than the "norm" but with the triple's it dosent need to be and can have pistons that last a lil longer/.
 

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Discussion Starter · #13 ·
Well it was suppose to go on the dyno today but when I called to confirm the time he said that his truck was broke into last night and he has to deal with that and all the others I called said one day notice was too short....maybe Saturday I will get it there. Sounds good while it's running in the garage!!!

The first pass will be with T5's and 28 PWK's then 35 PWK's then switch to CPI inframes with the 35's then throw some 39's on to finish it up.
 

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i put a set of cpi's on our lil gasser stock cylinder'd 350 sunday whoo hoo those pipes really like that lil motor combo took the t-5's off its got a lot more rpm acceleration, top end but still a lil lacking on the bottom should be good this spring for the dune racing. didnt know that lil motor could pull like that.. ( well its been a long time since it had drag pipes)

get that thing on the dyno and lets see it!!!
 

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I'd leave 35s on it.

What did you end up doing as far as port heights? What domes/pistons etc that will make a big difference. Make sure the domes will work right with the pistons you have. My old stock stroke cub ran better with T5s on it down low and 7 degrees of timing than with my CPIs. The CPIs had it on top. I think overall it was just as fast with the t5s. I'd like to see what you end up with. I have some real tight squish domes for a 573 series blaster piston in a 68 bore I had cut for a spaced cylinder. They are .017 step I think if you want to space the cylinder up they'll get the squish down over a .031 step dome. You could borrow em to try. 68 bore, 18cc, .017 dome. Radar
 

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Discussion Starter · #16 ·
I bought the cylinders used and they didn't come with pistons. I bought a set for the stock stroke cub, like 978 series or whatever they are and they came out with zero deck height and fit the cylinder great. I bought some domes from Tim at titan racing and I haven't checked the squish on them yet. I told him what I had and he cut them for me.

Final port durations are 128 intake and 196 exhaust and there's not much left between the extra exhaust ports and transfer so I hope I don't get much short circuiting with it.

It's my daughters bike so I want more torque out of the motor but want it fast when I ride it. I will end up with the T5's and 35's but I just want to know what it will make HP wise with the big carbs and CPI's. More to see what the work I did will do and if I ever go to sell them I can list that also.
 

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Discussion Starter · #17 ·
Well I just got back from dynoing the bike and here's what we got

With the T5's and 35 PWK's the most it made was 74HP and 39lbs of torque

we bolt the CPI inframes on and got 84.5HP with 35's and the CPI's and 46lbs of torque

We played with the timing a lot and here's what happened with +6 timing we got 84 Max HP

With +10 timing we got 71 HP with everything else the same

Moved it to +2 and made 78 Hp and finally settled with +4 for the most HP 84.5

We made a lot of pulls and I didn't go with the bigger carbs cause we just ran out of time.

I think there's a electrical issue cause I would think the more timing the more power it should make not loose power with a lot of timing.

So there you have it a stock stroke, stock rod Vito's cylinders with my very first port job running 128 transfers and 196 exhaust, V force 2 reeds, CPI's inframes, 35 PWK's on gas, with +4 timing made 84.52HP and 46lbs of torque

I wanted it in the 90's but what do you do......

The transfer size on these cylinders is just how you buy them. all I did was raise them up and the exhaust is just how they came but I did make the 2 sub exhaust ports bigger (in the tunnel) and deeper. I think by making the tranfer tunnels bigger would increase the numbers.

What do you think made the numbers drop with more timing? Bad stator maybe?
 

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Did you add more fuel to compensate for more timing? Sometimes you're not going to get the peak HP form more timing, you get bigger rush of HP at a lower RPM, but it signs off quicker.
You will not have as much over-rev either.

I wouldn't say it's an electrical problem, I'd just say you found the sweet spot for timing on that particular setup.

How much squish did you have, what was the squish band? how much uccr is there?
 
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