head specs - 800 ves

[Twostroke]

So I aquired what I was told was a "race gas" head for my 800 ves. Not much info was known on it, got it from the second owner. It's a stock head that has been milled or maybe more. Is there anyway that I can measure to know what has been done to it? It for sure has been "milled"/"shaved"/"decked", you can see it visually( I have other stock heads I compaired it to). The domes appear stock but it's hard to tell, it could have been massaged some.

I have a caliper, were these heads made well/tight enough that I can mic it to see how much exactly has been removed?

Could I send it to a someone with a better trained eye that would be able to tell me what's been done?

What was a typically amount that these were shaved?

 

[Scott]

Talk to Turbotater.

 

[Twostroke]

Thanks for the lead

 

[go high fast]

I would go with stock head cover and SLP cheater heads and domes. There is a wide range of choices.

 

[Twostroke]

I've been researching heads lately and then I remembered that I had this one in a box of 800ves parts I was gave with a motor I bought.

I'm thinking of doing a compression test with it and see what kind of psi it puts out, is their a breaking point where these motors need higher octane with higher psi? stock timing.

 

[Scott]

I've been researching heads lately and then I remembered that I had this one in a box of 800ves parts I was gave with a motor I bought.

I'm thinking of doing a compression test with it and see what kind of psi it puts out, is their a breaking point where these motors need higher octane with higher psi? stock timing.

Yes, there isn't a MAGIC bottom number, because it does depend on a couple of things within your motor...but if you are making 150 cold cranking compression then you likely will need some race fuel to raise the octane.

 

[Twostroke]

150psi at what altitude?


Kinda of leaning towards going big bore, but I'm curious to see what this head blows on the gauge vs my stocker. I'll try to make time this weekend.

 

[LoudHandle]

There is more to it than just compression, squish and chamber geometry come into play. Fastrax would be another source to consult on this.

 

[Scott]

150psi at what altitude?


Kinda of leaning towards going big bore, but I'm curious to see what this head blows on the gauge vs my stocker. I'll try to make time this weekend.

See below.
Can be ANY altitude.

There is more to it than just compression, squish and chamber geometry come into play. Fastrax would be another source to consult on this.

 

[Twostroke]

The was me joking

This head appears to just be decked..

 

[LoudHandle]

I would also double check the squish, less than 0.060" is bad news for detonation as I remember it but I am by no means an expert. I was just having issues with a mismatched engine and detonation and that is what I remember UBR recommendations were for my Race gas triple with pretty radical porting. UBR has been absorbed by Fastrax, hence my previous recommendation. As I purchased their domes and confirmed squish to be in tolerances, and had no further detonation issues.

 

[Twostroke]

My motor is miss-matched also, I have two of them so I'm constantly rebuilding and swapping certain parts. I will measure the squish when I test the compression of the head.

For testing squish do you guys normally just use some solder in the cylinder then spin the motor by hand to TDC to smash it then mic it?

I've talked with FTX before when I was running one of their odd ball 950 800bb based motors, knowledgeable guys, wish I wouldn't have seized that motor, it ripped..

 

[LoudHandle]

For testing squish do you guys normally just use some solder in the cylinder then spin the motor by hand to TDC to smash it then mic it?

Exactly, bend it about 70-80 degrees about 1 3/4-2" (roughly half the bore) from the end and insert thru the spark plug hole, feel for the upper corner of the cylinder / head interface and hold it there for a bit while you roll it past TDC. Extract and pull a few measurements, as it will likely not be parallel all the way across and should be then at the end of the solder so it squishes the flame front to the center of the dome rather than trapping it at the edge. Fastrax had a few You Tube videos on how to do a few of the more common tests like this but don't remember if this was one of them. I remember them cc'ing a head on and off the engine to calc. compression ratio in one of them. Might be worth a look if you have any doubts still.

 

[dropitp*ssy]

You can check the volume of the chamber without having to change it out and check compression. Easiest way would be just to get a syringe labeled in cc's and use it to see how much water it takes to fill the chamber. I believe the stock head is supposed to be 49cc's