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Wondering when you have to rebuild an engine. My xcr 700 has 100psi on all 3 cyl. should I rebuild top end before the snow or run for another year?

Thanks Bimmer1



:beerchug:
 

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Discussion Starter · #3 ·
Think I should leave it for this year, maybe re-build it next year?
 

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what kind of compression tester are you using?? different types give very different readings. if yours has a long hose between the gauge and head, it will give low readings. most gauges have paperwork explaining readings, to compensate for designs. normal compression should be 130-135 psi.
 

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Discussion Starter · #5 ·
I have about 5 inch. between the gauge and head, I think it's made by some German company.
 

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Originally posted by AKRAY4PLAY@Sep 12 2005, 03:29 PM
what kind of compression tester are you using?? different types give very different readings. if yours has a long hose between the gauge and head, it will give low readings. most gauges have paperwork explaining readings, to compensate for designs. normal compression should be 130-135 psi.
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Id try a different gauge to see if the readings are any different - your motor should be close to 125psi for normal compression. If its really 100lbs, then youre on the low side - does the motor have a lot of miles? Replace it with new rings and pistons. Anyone? WL ...
 

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Pull it over until the gauge will not go any higher. They should be within 10% of one another, but try another gauge. 100 is on the borderline of not running properly. Also if the pistons have started to collapse, you run the risk of breaking a skirt.
 

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Originally posted by bimmer1@Sep 12 2005, 11:59 AM
Wondering when you have to rebuild an engine. My xcr 700 has 100psi on all 3 cyl. should I rebuild top end before the snow or run for another year?

            Thanks Bimmer1
:beerchug:
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Use a second guage and compair them should be around 125 psi but look for them to be even. Have seen 2 different guages give a large variation between them. If its still on the low side pull your exhaust off and look at the pistons for blow-by below the rings or any scuffing on the skirts. Normal if the pistons are scuffed the compression is not even between the cylinders. If it has exhaust vavles you can pull the valves out and you can see the pistons without pulling the exhaust.
 

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Discussion Starter · #10 ·
I did hold the throttle open wide, should this be done when testing? I also have about 5100miles on it. How many miles before I should freshon it up?

I will also get another gauge to see if there is a difference.
 

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Originally posted by bimmer1@Sep 13 2005, 07:17 AM
I did hold the throttle open wide, should this be done when testing? I also have about 5100miles on it. How many miles before I should freshon it up?

I will also get another gauge to see if there is a difference.
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The throttle should be held wide open to allow as much air as possible to fill the cylinder.
 

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Crank it over 3-5 pulls at wide open when the gauage stops moving likely after 2-3 pulls. That motor can go for 15,000+ miles, many people have done that with no work on it. I know of XLT's that went 20,000 miles and 680's at 14,000+ so far. These motors are great (the 580 and 680 triples). Will be a difference between a cold and warm motor compression. Plus your sled starts with one hand with a very light pull on teh rope only a few inches where as teh guys ont eh tiwns need both hands and the feet on teh running boards to start thee sleds. Ah the mid range triples. The best motors in the business ask anyone who knows his stuff i.e. last the longest, give you the best throttle response and run the smoothest and sound the best plus give great gas mielage.

Ultra's beat many 700-800 twins on the lake both in stock form. Yes they are a few punds heavier eg. 506 stock.
 
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