no compression after rebild?????


24 replies to this topic
  • fastback959

Posted August 16, 2008 - 09:53 AM

#1

i replaced the rings, cam chain, adj the valves and all the gaskets. when installing the cams i have them e-i and e-i with the cyl at tdc. but when cranking the eng over, slowly i dont have a compression stroke, so i pulled out the decompression shaft thinking it was sticking open but that was not the problem. i thought that i might have one of the cams off and caused the exhaust to open to fast and caused this problem , but at compression stroke both cams are not even tuching the valves.???? when turning over the engine with a socket i can hear the intack sucking and the exhaust blowing , but i do hear the exhaust twice, one right after another, the first one is small and the one right after that sounds like it should.???????????? hellp?? grayracer513...... sorry, im working on a 2001 406 with stock cams.

  • desert-rat660

Posted August 16, 2008 - 10:42 AM

#2

your valves hanging open a bit?

  • fastback959

Posted August 16, 2008 - 11:00 AM

#3

next step i will recheck my valve clearance??? THIS SUCKS!!!!

  • desert-rat660

Posted August 16, 2008 - 11:04 AM

#4

Make Sure The Shims Didnt Come Loose Under The Valve Bucket, If It Did When U Bolted The Cam Down It Caused The Valve To Be Pushed Open

  • fastback959

Posted August 16, 2008 - 11:42 AM

#5

good thinking desert-rat!!! i can only hope!!

  • desert-rat660

Posted August 16, 2008 - 11:43 AM

#6

Do U Own A Service Manual For The Bike?

  • fastback959

Posted August 16, 2008 - 12:45 PM

#7

yea.... this is the 2nd 426 i have done.

  • grayracer513

Posted August 16, 2008 - 12:53 PM

#8

Lack of compression, assuming you installed the rings on the piston, is related to the valves. Your problem is probably either that the engine is timed wrong, or a shim is not seated in its pocket.

Check the marks on the flywheel against real TDC at the piston. If that's OK, recheck the timing and valve clearance. A titled shim will show up as no clearance.

  • Butta

Posted August 16, 2008 - 01:26 PM

#9

i replaced the rings, cam chain, adj the valves and all the gaskets. when installing the cams i have them e-i and e-i with the cyl at tdc. but when cranking the eng over, slowly i dont have a compression stroke, so i pulled out the decompression shaft thinking it was sticking open but that was not the problem. i thought that i might have one of the cams off and caused the exhaust to open to fast and caused this problem , but at compression stroke both cams are not even tuching the valves.???? when turning over the engine with a socket i can hear the intack sucking and the exhaust blowing , but i do hear the exhaust twice, one right after another, the first one is small and the one right after that sounds like it should.???????????? hellp?? grayracer513...... sorry, im working on a 2001 406 with stock cams.



Sorry, I have to ask the stupid question, just because I've seen these answer my own problems......did you install the spark plug when doing your "compression" strokes?

  • fastback959

Posted August 16, 2008 - 01:44 PM

#10

rings are on the piston and set up right. and the spark plug is in it. i haven't got to work on the bike yet but im hoping it is a shim not seated...like the desert-rat stated.... this is only the 2nd thumper i have worked on, but im a 8year ase tech and subaru certified tech for 9years.

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  • desert-rat660

Posted August 16, 2008 - 01:50 PM

#11

i work for nissan as a tech, the valvetrains in these bikes are similar to whats in the cars i work on everyday, only difference is we never have to check the valve clearances. same design though, bucket and shim...

  • desert-rat660

Posted August 16, 2008 - 01:51 PM

#12

hey fastback how do u like your r6? i have an 05 raven

  • fastback959

Posted August 16, 2008 - 06:09 PM

#13

i like the r6 its runs good, for a 600. it ran a 11.2 at 124mph up in the Montana's air. im happy with it. well bad news i got back to the bike today and i have 0.11mm on the intake and 0.21 on the exhaust. spec is 0.10-0.15 intake and 0.20-.025 exhaust. i know i set the rings up right!!! i have saw posts about bikes that had good compression one day, and then it felt like you would kick it with no plug the next. whats that all about??

  • 1998YZ400F

Posted August 16, 2008 - 06:19 PM

#14

you could do a leakdown test to determine where its leaking

  • desert-rat660

Posted August 16, 2008 - 06:46 PM

#15

u sure the timing is set up right?

  • fastback959

Posted August 16, 2008 - 07:46 PM

#16

i think I'm going to try to post a photo. But on the fly wheel i have three lines on the top of the flywheel, if I turn the crank counter clockwise you would see two lines, the first one would be two latitude lines with a connecting line in between them like this " l-l " just past that, going counter clockwise i have one more line. So together I would see " l-l l ". I have the cams set "E-I" on the exhaust and "E-I" on the intake cam lined up with the sealing side of the valve cover to the head, with the cams lined up, my crank lines up with the timing plug in between the two with the connecting lines.

  • desert-rat660

Posted August 16, 2008 - 07:55 PM

#17

it should be dead on with the (I) mark, cam lobes should be facing opposite eachother with lower mark flush with top of the head

  • fastback959

Posted August 16, 2008 - 07:59 PM

#18

so i need to set the cams up with the single line not the two connecting ones??

  • grayracer513

Posted August 16, 2008 - 08:55 PM

#19

so i need to set the cams up with the single line not the two connecting ones??

Yes, but you should also verify that the "I" is actually TDC by checking the piston position with a probe in the spark plug hole.

Have you verified that you have valve clearance?

  • fastback959

Posted August 16, 2008 - 09:13 PM

#20

i have 0.11mm on the intake and 0.21 on the exhaust. spec is 0.10-0.15 intake and 0.20-.025 exhaust. when i recheck it i will set a long piece of soldering rod in the cylinder and check for sure... with the way i have it now the exhaust valves would open to fast. and would blow my compression out the window. right?





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