Compression questions

[longnosetrucker]

Hello fellow riders ive have a freshly top end rebuild on my blaster the bike runs great start great first or second kick but heres the thing i put a compression tester on that i had just boughten and im getting a reading of 110 psi engine was warmed up for about 5 mins the exhausht was warm engine little less then warm with about 4 kicks and wide open throttle should i be concerned also thike bike has never been bored over just regular piston and ring change for matinence never been blown up am i in the right psi range being at 110 ?? Thanks

 

[Awk08]

did you kick it until the needle stopped moving ?
110 is a little low, but acceptable.
a fresh bore/piston should be 120+
since you replaced just piston/rings into a worn bore, 110 sounds about right.
just keep an eye on it as it drops to around 100, it'll be time for an overbore/piston

 

[speedyslyder]

head mod will bump up compression lol.
gauge may be off but who knows.
keep an eye on it
mine sayed 120psi and it still needed to be freshend up when first purchased

 

[longnosetrucker]

The cylinder and and head are in mint shape just always replaced the pistin and rings just every 15 or so hours and never actually riddin it hard lol barely ever saw 6th gear and just never really paid attention to the compresson but runs amazing no lack of power just could find the specs for a stock 98 blaster lol but ill keep an eye on the compression for shure its always felt low im an adult so i dont really feel the resitance like being on a dirt bike lol

 

[longnosetrucker]

Almost bought 4 inch riser for it today has any one ever put riser on an atv but used a piece of another set of handle bars to mount them hard to explain but would it work instead of buying the adapter piece scared it wouldnt be as durable as a solid chunk of steel

 

[longnosetrucker]

Also would a port and polish lower or raise your compression ?? Ive herd both lol so i dont really know

 

[speedyslyder]

i raised my exhaust port 1mm and compression did not change?
then i had ken do the head mod...cost me 85 dollars total for shipping there/back and his crafty skills.
bumped my compression up to 150psi

http://www.kenoconnorracing.com/

 

[longnosetrucker]

Well i guess ill just have to keep an eye on it dont wanna tear a apart a good running bike but when i do im going to go all put in there lol but first im going to be using 6th gear alot more this spring guess the saying is true dont use it youll still lose it bahaha over maintained in the wrong ways i suppose things still get worn out

 

[Blaaster]

It is pretty normal for the compression to be lower than expected when fitting new rings.

Until the heat cycles have been done and a few rides have been made there will be some blow by until the rings bed into the new crosshatching, ( I am presuming the cylinder was honed)

The compression should raise if indeed honing was performed,

if no honing was done it may take some time for the rings to bed, but the problem with no crosshatching is that the rings will not get adequate lubrication and may wear out very quickly.

Rings rely on oil trapped in the scores to lubricate them.

 

[jus_me]

A raised exhaust port would usually lower compression. It is usually then is compensated by shaving and or re chambering the head (cant shave too much though!) The typical Blaster is very conservative in the squish. Squish is the thickness of the air gap between the piston crown and cylinder head when the piston is at top dead center. A proper squish will bump up compression there for increasing hp. A head re chamber is really the best cheapest mod you can do to a blaster.

What comp tester are you using?

 

[longnosetrucker]

I used a trisco compresion tester bought from royal distributing also yes the honning was done but on the plus side it really hasnt been out since rebuild beside a couple of laps around the back yard this winter also port and polished head on it

 

[joeak47]

Here's a link to one of my old threads...
http://www.blasterforum.com/threads...ts-your-altitude-sound-off.50234/#post-633834
What altitude are you at? You need to compensate the reading your getting by adding 3.4% for every 1000ft in altitude. Hope this helps.