ok guys, so heres a little back story.i have a rephased and big bored xs650 with rd springs and pamco 277 ignition and pma and all that jazz. well i decided to go for a ground megacycle rephased cam. while it was torn down i took my head to a performance motor shop along with some kibblewhite guides and stems and all new seals for the valves as well. so i got my cam in and my heads back. get them installed. i was told to install the cam just like stock and just like hugh says to do since its rephased. and use that tick as the alignment mark while the left cylinder is at TDC. so i do all that and get it all in and everything else. now it won't fire. i checked the spark. i checked the battery (yes i know i have a pma but i run a super small battery in my box so my lights don't dim way down at a red light). its getting gas, and its getting air, and its getting spark. and when i spray starter fluid in it, it just back fires really loud and thats it. and won't turn on. everything i check keeps pointing me in the direction of the cam timing is off...but i installed it exactly how they told me to, and there is no way to degree the sprocket in because its solid piece. but i tried putting my timing plate for my ignition in every position and nothing. i have no damn idea whats going on...has anybody put a megacycle rephased cam in their 650??? did they have similar issues??? need help.
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Starting issues!
- Thread starter mattg666
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and i also checked my plugs and re installed my ignition to check for the third time i didn't put something in wrong even though I've uninstalled and installed that ignition so many times i know whats up with it….i can't for the life of me figure this out.
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your cam timing must be off 
Put your LH cylinder piston at TDC on the compression stoke check that your rotor is at the TDC mark .
Then remove your valve covers on the LH side and check that both valves are fully closed and the tappets are both loose .
Then do the same for the right hand cylinder at TDC on its compression stroke.
Put your LH cylinder piston at TDC on the compression stoke check that your rotor is at the TDC mark .
Then remove your valve covers on the LH side and check that both valves are fully closed and the tappets are both loose .
Then do the same for the right hand cylinder at TDC on its compression stroke.
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with a mate and a timing light you should be able to check spark timing while kicking it over, having the plugs out would help do this. 145 seems a bit low on a hot rod set up which with a backfire might point at the cam timing being off. Did you use a degree wheel on the crank and check the valve action?
The cam sprocket is press fit on the cam, valve timing is moved by pressing it off and on the cam. So you need to confirm that the sprocket was timed to the cam at the shop. Peanut's procedure should confirm you are at least in the ball park.
The cam sprocket is press fit on the cam, valve timing is moved by pressing it off and on the cam. So you need to confirm that the sprocket was timed to the cam at the shop. Peanut's procedure should confirm you are at least in the ball park.
would it make a difference if the camshaft was reversed ? Are the lobes symetrical or asymetrical ...I know nothing about rephased motors to be honest . lets hope the machine shop got the sprocket placement correct.
Heres a link to Howard's Smedspeed site for everything you'd ever want to know about the math behind rephased cranks and cams........ groan....
http://www.smedspeed.co.uk/tech.html
Heres a link to Howard's Smedspeed site for everything you'd ever want to know about the math behind rephased cranks and cams........ groan....
http://www.smedspeed.co.uk/tech.html
DIRTY DOG
XS650 Guru
I have done w few rephased eng' and it sounds like the cam need's degreed in. it's not that hard to do,a little heat on the cam gear makes it go on and off easy'er
once again guys, this is a megacycle cam..its welded... can't degree it in like a normal cam. so i guess i gotta pull the motor again and see but i was told by some known people that it was degreed to install to stock specs and thats what i did. and I've installed and uninstalled a cam several times so I'm not new to it. its just not making any sense as to why i would be told to install it to stock specs if that were not the case.
have you done the checks that I suggested ? do you see the point of it ?
You are going to know for sure if you have a cam timing issue without involving a lot of possibly unnecessary work.
you certainly don't want to strip the engine just yet without making that basic check .
do you see the point of it ?You are going to know for sure if you have a cam timing issue without involving a lot of possibly unnecessary work.
you certainly don't want to strip the engine just yet without making that basic check .
Did you do peanut's suggestion? You should be able to gauge if the cam is where it should be by comparing the the angle from TDC that the intake and exhaust ramps cause the tappets to start to lift. check this on both sides.
Guess this is a plus one cross post. grin
Guess this is a plus one cross post. grin
next up get a timing light see if the spark is where it should be. hmmm with a 277 pamco and two coils I'll guess the pamco rotor could be 180 out of phase.... the advance rod can be turned 180 on the RH end.
i triple checked it all with the ignition. the pin is on top and the mount for the advancers is all the way on the pin and in the right spot, the advancers are facing the right direction and the end of the rod mark lines uo with the mark on the advancer mounting bracket. and the pin is in the right spot on the other side and the rod and the magnets are both parallel with my engine case, just like it says. followed them verbatim and completely redid it just to triple check. and again, one of those things I've uninstalled and installed several times so I'm not new to it….its really just driving me nuts
Yup need two without a starter. I would turn the advance rod 180 and try again. (I think) that unlike a normal pamco the 277 rotor can be 180 off.
http://www.yamahaxs650.com/277_rotor_installation.htm
Npote pete's warning about how many ways this can be installed wrong!
Npote pete's warning about how many ways this can be installed wrong!
ok, tried the ignition ever way possible, flipped it 180 degrees and nothing, and then tried using the other key hole on the magnetic triggers since on hughes thing he says one key is for machined cams and the other is for ground, or what have you…and nothing, tried them both with the rod normal and with it 180 degrees….and now i don't even get a back fire with starter fluid…i don't know what the hell is going on
DIRTY DOG
XS650 Guru
3-things- 1 do you have a pic of the cam, I have used megacycle cams before and have never had one welded, 2 sorry if I missed this but are you sure the pamco is wired to the correct coil ? 3 I had same problem and it was the pamco adv.rod timming I think 1 pin needed to be up and the had to be dowm 180*apart ( the little locating pins)
