How much is to much compression? Please make suggestions...

B

Brett Corwin

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Joined
Aug 3, 2004
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39
Age
62
Location
Finger Lakes area, NY
How much is to much compression in a SXR700 motor? I posted the compressin as 145-151lbs warm and with throttle wide open. In a garage at about 55 deg's, it was in there for a couple of hour prior to doing the test. Only 3 full pulls (throttles wide open) and we got 157lbs. to 161lbs on all 3 cylinders. I will check it with another gauge....

Until then is that to much compession? I'm not boasting about the compression! I'm worried about it being to high! I check the gauge then double checked it! I just want a good running sled with some get up and go! Reliable and fun thats all. The compession was that high when I bought it. The head is not cut, the jugs are and the exhaust ports are ported.

Piolet jets are 145.... do they need to be larger? I'm riding at around 1500' to 2200' elevation.

Should I cut the reed stops? There are carbon fiber reeds installed already. Should I go back to the stock reeds if I cut the reed stops??

Factory pipe and can. I cut the can as suggested by some of the members here.

Installing a Boost Bottle from Hauck and a clutch kit stage #3 from Hauck (set to my weight 280lbs with gear and aggressive trail riding style).

Please make suggestions. This is my first Yamaha and I really don't know the in's and out's with this sled!

Thanks all,

Brett


:2strokes: :letitsnow :yrules:
 
if the head isn't cut, most likely then took out the middle layer of the head gasket, to raise the compression. your pilots jets aren't 145.....those are the main jets. you could cut the upper reed stoppers ONLY, like in the tech pages, but only if it doesn't already have reed spacers. if you cut the upper reed stoppers, you can still leave the carbon fiber petals in there. also, i wouldn't waste the $$$ on a hauck boost bottle or their clutch kit. just setup your sled to one of turk's setups in the tech pages and call it a day.
 
mopar1rules said:
if the head isn't cut, most likely then took out the middle layer of the head gasket, to raise the compression. your pilots jets aren't 145.....those are the main jets. you could cut the upper reed stoppers ONLY, like in the tech pages, but only if it doesn't already have reed spacers. if you cut the upper reed stoppers, you can still leave the carbon fiber petals in there. also, i wouldn't waste the $$$ on a hauck boost bottle or their clutch kit. just setup your sled to one of turk's setups in the tech pages and call it a day.
Click to expand...

Turk told me you can't cut the heads....

Yes, I ment mains, not pilot.

Gaskets have all three layers rivets are in place.

The clutch kit I bought before finding Turk's tech post on clutching.

You don't think the boost bottle kit is worth the money? I would have to have the bottle fabricated and buy the boots anyway.. So it seemed to be reasonable to just buy the boost bottle kit. It came with everything.

What about the compression? To high?
 
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my compression checks in at 125 on my guage, and when the motor is cold, the first pull is pretty hard, and slow, the second it better, and then it usually lights up on the third. With the compression you're getting, you'll need all that 280 just to pull er over!
 
dwarf717 said:
my compression checks in at 125 on my guage, and when the motor is cold, the first pull is pretty hard, and slow, the second it better, and then it usually lights up on the third. With the compression you're getting, you'll need all that 280 just to pull er over!
Click to expand...

Yes it takes strong pull but startes on one or two everytime.
 
On my sxr, I had the head milled .020 about 5k miles ago. No problems since. I prefer to use the OEM head gasket complete. Al
 
i never ever did say you can not cut the heads. i said the heads are hard to cut uniformly & it is easier to deck the top of the cylinders. please quote me correctly!!!!
 
Compression gauges change from unit to unit. Best thing to do would be to check the squish and post what it measures, the engine guys on here will tell you if you are safe or not.
 
My appoligies Turk...

Turk said:
i never ever did say you can not cut the heads. i said the heads are hard to cut uniformly & it is easier to deck the top of the cylinders. please quote me correctly!!!!
Click to expand...

My appoligies Turk... Turk said, for verbatim "The monoblock head is amazingly hard to get an even cut across. Never even seen it done.Most guys decked the top of the cylinders as it,s a lot easier & consistent".

Per this statement I understood it couldn't be done...

:die: My error! :dunno:
 
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francis6667 said:
wath is the minimum squich we can have on a red head motor 700?
Click to expand...


francis6667, I'm glad you asked...! I was hoping to find that out also. It would be great if we got answers...... instead of comments. The comments are appreciated but answers would be more helpful! :dunno: I'm not :bash: anyone, just hoping for answers.

Again francis6667 thank you for asking that question, lets see who answers... I have yet to have anyone answer "How my Compression is to much"..? a number would be great!


:letitsnow
 
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I believe .060" with the headgasket in place. IF I remember correctly this is what Mr.Viper had mentioned in the past- But am unsure if it was for the SRX/VIPER or for a Red Head motor or if common for both. If you go to tight on squish you run into a Detonation problem.
 
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I have 2 Sxs and have set them up with a stock single exhaust and with tripples as well as two seasons with a BB 800, here's some of my suggestions.

When using the stock single exhaust:
-don't waste your money on a boost bottle
-installing reed spacers is a MUST
-use Carbon tech reeds in the stock cages[no need for Vforce]
-1 layer off of the head gasket works very well with stock head and premium fuel-
-I also had good luck with the airbox mods but a lot of people will not agree with me here[tech pages]
-adjustable transfer rods are a must
-a good 1" track I found to be the best all around compromise and does not create any clearance issues
-if you have no noise restrictions issues, I found modifying the exhaust canister to help performance a bit[tech pages]
-with stock porting and single exhaust these redhead tripples have a very flat/forgiving power curve but mine ran best when clutched to shift out at a MIN of 8300 and a MAX of 8500RPM
-I found the 99 700 SX to be geared pretty well right on at 23/40 although I occasionally used 22/40...both worked well just depends on conditions
-once you have all the other work done work on the clutching...these SXs really like to over rev with the stock setup. I found both of our 600 + 700 SXs would pull a lot more primary weight and or secondary helix angle then stock...the tech pages have recommendations on this, I no longer have the notes on my setup but I do remember that I only added weight to the tips of the stock weights.

These SXs really do work well with a single pipe when properly set up.

JM.02c

Bob
 
On your compression readings:
-the stock SXs usually had compression readings in the 120-125 range
-your compression readings are high but guages can vary quite a bit
-run the sled for awhile then check your compression and see what you get
-get another guage from a buddy and check your compression again
-if your readings are high then I would say the head has been cut

Turk: Les in Winnipeg has cut a couple head surfaces for my Red Heads for me as well as BB + squish angle changes.

Bob
 
My redhead, with a single pipe has seen 107 mph on radar with the stock track studded. 104 mph with the 11/4" track studded. They can work very well. My sx700r works even better on trail, and awesome bangin'!
 
On Squish:

The stock squish on my 700SX was : .074"
Removing one layer of gasket[.010"] will bring squish to : .064"

As a side note: removing .001" off the cylinder head or gasket will increase the cranking compression by approx 1 lb.
Ex: remove one layer of head gasket reduces squish by .010" and increases cranking compression by approx 10 lbs...this is the MAX I would do on a trail motor!

JM.02c

Bob
 
My 98 xtcp700 blew 135 per cyl w the stock gasket when I tested it last night, Bluemonster1s sxr600 blew 140-145psi w a new motor and 1 layer of headgasket.
 
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