670 primary spring

[prairieguy]

whats the best spring to run? after market or stock?

i don't really want a high engagment. i was just wondering what you guys have run and had good luck with.

stock 670 with 136

thanks
joe

 

[winter brew]

The answer depends on the rest of the settup, altitude etc.... Doo springs work fine, they have a large selection.

 

[prairieguy]

well i drive under 3000 ft
have hollow pins

secondary
50 deg helix
maroon spring



it sucks going to school and trying to work on a sled living in the doorms away from home!

 

[prairieguy]

i was wondering if anyone has found a spring chart showing the differences in the springs?

is 110- 105 bad on compression for my 670? does anyone know of hand the ring gap for my rings? i'm running amzoil could that oil lower compression or no?

thanks for all the help
joe

 

[winter brew]

Sounds low if your close to sea-level, should be closer to 135.

 

[prairieguy]

so maybe i should be looking towards comprssion for not having full top end rmp?

 

[skidoome]

From all the ring boxes I have looked at they recomend .004-.007 per inch of bore.... So the tightest they recomend would be around .012. I do a touch larger.

Compression on my stock 98x is 135 at 4000 feet if your engine has more then 300 miles on a fresh rebuild amsoil will not lower compression. It just takes more time for the rings to seat if you use fully synthetic oil after a rebuild. I have found that about 250 miles or 5-6 trips my 98x and 99x started to gain compression and run a bit better. I rebult my 99x last year and started with 125lbs. cold. then after 5-6 trips it went up to 150 ish.

good luck and where are you from?
jon

 

[prairieguy]

i just checked the compression again and cold it says 120psi. at work a freind just rebuild his summit x and cold he had 145psi and warm was around 135psi. so i pulled the engine apart and ring gap is .017 tho and .o19 it seems still alittle tight but not good enough. i have no clue how many miles this engine i bought it off a guy who bought it used so i think i'm going to maybe bore it over one size and put some new molly coated SPI pistons in? what you guys think or just rehach and new pistons and rings?

thanks for all the help
joe lukan

 

[Skidoohmx]

Which 670 do you have if it is a 98 99 670 X motor your compression is low. If it is a non HO 670 from like a 97 summit they were lower and your numbers aren't that far off, especially if they are near the same. Those motors seemed to wear the pistons out alot sooner than wearing the cylinder so I would just rehone the cylinders and replace pistons & rings unless you see something that does not hone out.

 

[prairieguy]

the engine is out of a 98 mxz

i have a manual for 99 and they say the 99 mxz where HO but not the 98?
also what about in the section "technical data" the jetting that is show for the sleds does anyone know what elevation it is for? would a 99 formula Z 670 be close to a 98 mxz 670?


thanks
joe