RIVA Head issues! Take a look:

[YamahaBOY]

Hey, i just bought a ski and started taking it apart and looking a little closer... The cylinders are stock bore, but it has 84mm domes in the head! I take it that is a 760 head? Will that work on the standard bore ? Is there even any difference between the two? It looks like the o-rings should seat just fine, and everything else matches up wonderfully. I'm pretty sure that the motor has plenty of hours on it with that head. Any comments?

 

[Matt_E]

Should work fine, I would think.

 

[YamahaBOY]

Yeah, i was thinking that, it appears that everything was seating properly but i wanted to ask for other people's opinions first. Anyone know the differences between the 701 and 760 aftermarket heads?

 

[bad93blaster]

the 701 dome are 81s and 760 are 84s you might get alittle deto

 

[Matt_E]

Why?

 

[YamahaBOY]

They are 38cc domes, and from what people say you can run as small as like 36 on pump gas.

 

[sflsurfrider]

if the domes are replacable, why not just buy new domes and do it right? theres a reason they make the domes' diameters match the bores.

if theyre not replacable domes, sell the head and get the right one.

just my humble, as always, opinion.

 

[DAG]

i have rivia 35 domes running 93 pump gass

 

[keefer]

The 84mm domes are 38cc to make 180lbs for that bore. The 81mm domes are 35cc to make the same comp for that bore. I would think that using 84mm domes in a 81mm setup would lower the compression and deto would not be a problem.

 

[sflsurfrider]

i wouldnt say to change them out of concern of deto. im just thinking of the funked up shape of the combustion area and how inefficient it could be. domes are cheap. do it right.

 

[Matt_E]

The 84mm domes are 38cc to make 180lbs for that bore. The 81mm domes are 35cc to make the same comp for that bore. I would think that using 84mm domes in a 81mm setup would lower the compression and deto would not be a problem.

Hence my confused "WHY???" :biggthumpup:

i wouldnt say to change them out of concern of deto. im just thinking of the funked up shape of the combustion area and how inefficient it could be. domes are cheap. do it right.

The shape is the same. Just a bit bigger. That said, I'd get new domes.

 

[sflsurfrider]

Hence my confused "WHY???" :biggthumpup:




The shape is the same. Just a bit bigger. That said, I'd get new domes.

i mean the entire shape... including the top (horizontal surface) of the sleeves. they shouldnt be part of the combustion area. at least in my warped mind they shouldnt. :dunno:

 

[Matt_E]

Better not run 701 domes on an 81mm bore then either, Charlie....701 domes are good up to 83mm (735cc or something).

 

[sflsurfrider]

troo!

 

[YamahaBOY]

It's a riva head. Now will the body and top plate accept the different domes (81 and 84 both)? I have no clue...

 

[Matt_E]

Should work.

 

[sflsurfrider]

itll work with the right size domes.

 

[YamahaBOY]

thanks guys for the info