Blowing orings

[4mildkue]

I have a noss head with 17cc domes on a 4mil alky motor an for some reasons it keeps blowing orings...the motor is brand new I just don't know why it keeps blowing orings in the head....any suggestions???

[Nightmare]

i heard something about noss heads blowing o rings out, cant remember if it was on here or another forum. ive ran one and never had problems.

[dlnoss]

Could you be detonating? I ask mainly because of the 17cc domes? If you are detonating, something will give like the spark plugs backing out, blowing orings, or grenading the engine.....the first two are cheaper..

 

What is the kicking compression?

[locogato11283]

17cc domes?! What is your elevation? Like David asked, what is your compression?

[4mildkue]

It does back my plugs out after every ride and my kicking compression was 185 and my elevation is 203ft

[locogato11283]

It does back my plugs out after every ride and my kicking compression was 185 and my elevation is 203ft

 

Then you have issues. You never thought that something might be wrong?!

[4mildkue]

Yeah Im just trying to figure it out I pulled the head and cylinders off the pistons and stuff still looks brand new and my cylinders are not scared...do you think if I went to 19cc domes it would prevent this?? Or do I need to switch my head and my domes

[locogato11283]

The head is fine. You need to get the correct domes. Who built the motor? You can contact David Noss for the correct domes once you figure out what you need.

[n2otoofast4u]

Ok so this is all just general obvservation from your recent posts about alky. It seems that your new to alky correct? 180 is a bit high, however it is usable if your setup is spot on. There is MUCH more to a dome than a simple cc #. So here is a list of questions most are gonna ask. If I were you I would copy/paste and then answer them. Thats going to yeild you the best answers.

 

1- Are the domes a shelf dome or did your builder set them up for you?

2- What is your squish?

3- How far are you running before it knocks the plugs out of it?

4- Does it "lay over" or suddenly drop out of power going down the track? (lean condition)

5- What do the plugs look like after it knocks them out?

6- What motor/carb combo are you running?

7- What position are your PJs in?

8- Does the bike try to "run away" or free rev after you pull the clutch in at the end of your pass?

9- Whats the water temp after you make a pass?

 

IMO this doesnt have anything to do with the head, and all to do with your tunning (or lack thereof)

[dlnoss]

timing also,

[4mildkue]

My domes are shelf domes,, i can make Abt 3 passes and it blows the plugs out,, it doesn't lay over at all,, and my motor is 4mil drag ported stock cylinder on alky with 38mm keihin carbs timing set at 9 degrees,,, it doesn't drop out of the powerband,, and it doesnt rev up by itself after I pull the clutch in...and my left cylinder usually runs Abt 120 and the right side is Abt 85 to 90

[n2otoofast4u]

timing also,

 

How the F did I forget that? Yes timing is gonna need to be known also.

[dlnoss]

There might be issues besides tuning causing the orings to blow but I might try backing the timing off (9 degrees is quite a bit of advance). The fact that it is

also blowing the plugs out points pretty strong at detonation. 'Shelf' domes are usually safe with alky domes but alky domes

aren't terribly safe with gas, (race or otherwise). The domes are 4mill 17cc? Did I make them?

[4mildkue]

I bought the head and domes off eBay the guy said the were noss domes and that noss cut them but Im having trouble with them maybe he was lying but I have some 20cc domes but there not cut I was thinking about having them cut and trying those

[n2otoofast4u]

I bought the head and domes off eBay

 

 

ENOUGH SAID... YOU TRIED TO SAVE 40 BUCKS ON A MOTOR THAT COSTS 1000S... RATHER THAN BUY IT FROM A BUILDER WHO CAN SET THEM UP FOR WHAT YOU NEED YOU LISTEN TO SOME SMUCK ON EBAY.. UNREAL!!!!!!!!!!!!!!!!! CALL A BUILDER, GIVE THEM YOUR ENTIRE SETUP, AND HAVE THEM CUT YOU NEW DOMES..