setting valve timing


14 replies to this topic
  • xroldie

Posted June 26, 2004 - 10:22 PM

#1

no i do not know how to do this at all.. but i know it needs to be done.. cam chain was loose and had the engine upside down chain moved a few teeth and now there no compression.. so i need to get it back to what it was befor. so can some1 please tell me or point me in the derection of step by step instructions for readjusting it back to what it need to be set to.. BTW its a xr 75

  • skipn8r

Posted June 27, 2004 - 03:06 PM

#2

All I have is from an '04 CRF80/100 manual. I assume you have the valve cover and left crank case off.

1) Turn crank counterclockwise and set piston to TDC.
2) Align cam sprocket so that two sprocket bolts are in line with the top of the cylinder and the "O" on the sprocket is up.
3) Install cam chain.
4) Tighten cam sprocket bolts to 12 Nm, 9 ft-lb.
5) The '04 models have an automatic cam chain tensioner. It's the bolt/nut on the back side of the cylinder toward the bottom. When the cam chain is on correctly, loosen this nut, the tighten to 12 Nm, 9 ft-lb.

I don't know if you have the same markings. Good luck.

  • xroldie

Posted June 27, 2004 - 07:29 PM

#3

ya i accualy red that somewere today.. bt i dont know how to remove the chain and put it back on.. does it have a master link liek the drive chain.. or .. ah i donno hepl me please

  • skipn8r

Posted June 28, 2004 - 03:45 AM

#4

I have not done this on an XR-75 before, so I'd assume you need to release the cam chain tensioner, then you could move the chain more freely. If not, remove the upper cam sprocket bolts, remove the sprocket, align it correctly, reattach.

  • Jetster220

Posted June 28, 2004 - 04:19 AM

#5

Well, Im not totally sure about a xr75 motor, but when I replaced the timing chain on my xr50, there is a cover behind the flywheel that you have to remove. And the timing chain doesnt have a master link, so it has to come out as one. The reason I think you may have to take it out from behind the flywheel is because you cant get it off the crank gear through the topend, and especially would not be able to get a new one back on.

  • xroldie

Posted June 28, 2004 - 10:08 AM

#6

ya this chain is fine.. the guy befor me didnt have the tensioner set right.. so when i had the motor upside down to clean it.. the chain jumped around.. and lost timing

so i dont need to takeit off.. but witout goin back and lookin at the bike.. i think i did see a plate behinfd the flywhell.. neway im off to go cheak it out..

  • Jetster220

Posted June 28, 2004 - 10:11 AM

#7

Well then you should be okay as long as the chain still is on the crank sprocket and didnt get stuck off it. If thats the case then like was said earlier you simply need to get the motor to top dead center and retime it at the cam with the cam sprocket and the timing marks. Good luck, and let know if you have any other problems and Im always here to help.

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  • xroldie

Posted June 28, 2004 - 12:48 PM

#8

whell i got it all timed right.. lined the "T" on the flywhell with the markon the case. and the "O" on the cam gear right at the top and got the chain back on... and now at about 1/4 throttle.. it just dies and put put put then shuts off... so i dono what to do.. and befor i retimed it.. it did the same thign at about 1/2 throttle..

  • Jetster220

Posted June 28, 2004 - 03:07 PM

#9

Have you tried checking your ignition timing with the points. I just remembered that my friends z50 did the same thing and it wasnt his valve timing but his igintion.

  • xroldie

Posted June 28, 2004 - 07:00 PM

#10

whell if i knew how to cheak those. and set those.. i woodent be asking this question.... how do i cheak and set the ignition timing??

  • Jetster220

Posted June 29, 2004 - 03:12 AM

#11

Alright, this one you are probably going to need a manual or somebody who knows the clearances and stuff for the points to do. But I can help you out some. First you are going to need a feeler guage so you can measure the gap between the points. You need to rotate the flywheel till the T mark is lined up and then you will have to measure the gap in the points and it should only be so much but I dont know what that is on the xr75 motor. Then you simply take a screwdriver and loosen the screw on the points and you can adjust it to set the gap at what it needs to be. If you need a manual here is a really good on to get. Honda TrailBikes XR75

  • xroldie

Posted June 29, 2004 - 01:45 PM

#12

ya accualy my gandad and grandma came over today for a suprose vist.. hes the one that gave me the bike.. and it turns out hes got a manual.. so next time i go out there ill get it.. but to tell ya the truth.. it sounds liek its floddin.. and not somethign to do with the ignition timing.. but i dont know.. just IMO

  • Jetster220

Posted June 29, 2004 - 02:09 PM

#13

Hm, why didnt I think of that, but I think you may be right. Do you have a new plug to try in it and see how it looks when you run it to 1/4 throttle and it shuts off. A good plug check can tell alot of things :thumbsup:.

  • xroldie

Posted June 29, 2004 - 02:23 PM

#14

whell see.. i kinda forgot to mention thi sin the last post.. but the iontake boot..whenn it kinda fell apart.. and now instead of buying a new one.. casue im a cheap ass.. i just but a piece of copper pipe in to bridge the gap.. and a couple claps to hold it tight.. and no theres no leaks... i can guere=ntee u that.. but what there is.. is a little "lip" casue the pip obviopsly had to fitinsed the intake boot.. so it does fight.. and just.. but the lip.. im thinking .. ( i have no clue.. just a thery) is that when u give it throttle.. the gas just kind of builds up around the lip.. and the sorta of "trickels" into the combustion chamber.. just a theroy tho.. but im gonna buy a new boot.. 20$ flat from a salvage place here in town.. so ill let ya know how that works out..

  • Jetster220

Posted June 29, 2004 - 02:29 PM

#15

I dont really think that is the problem, but definetly get that new boot lol.





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