Too hard to pull start

[Stephen115]

I'm experiencing alot of compression when pull starting, at times its so much it pulls the bike off the ground. but when I get it started it runs great. any ideas? I added the .265 lift cam and flat top piston. Its also spitting fuel out the carb at times when pull starting. I thought it might be the valve lash but I checked it and its fine. The cam has a compression release so I would think that would help this not happen, is there a point where you get too modified to where you have to have a starter?

 

[Txpowdercoater]

nope, you have issues with either the comp release mech is not swinging away or over properly oooor, the valve lash is incorrect

 

[Stephen115]

nope, you have issues with either the comp release mech is not swinging away or over properly oooor, the valve lash is incorrect

How do you tell if the release mech is working? and if its not, how can I fix it?

 

[buckeye]

You can tell when you pull the string and it pulls the bike off the ground:laugh:.

Something isn't lined up. Or, like suggested valve lash isn't quite right.

 

[Txpowdercoater]

I would start with making sure the valves are adjusted properly, recheck...then if still the same issues, drop the side cover off and check the movement of the arm. I had one that was tweaked and it did the same thing, my bike would pull your fingers off your hand! I checked and sure enough, the ramp wasnt swinging out to contact the lifter...take it apart and you will understand what I'm saying.
the way it works is a small bump swings via spring pressure into the path of the exhaust lifter, it barely opens the exhaust valve to release compression, barely but enough to start, when its running, centrifugal force keeps the "ramp" slung out of the way.

 

[Stephen115]

I adjusted the valves and it pulls like it should. It started up great but now it's having problems starting...

 

[67tempest]

Never had one apart. Is it possible that with the valves misadjusted the piston hit a valve and damaged it?

 

[Stephen115]

Never had one apart. Is it possible that with the valves misadjusted the piston hit a valve and damaged it?

I don't think that's it cause It idled for a couple of minutes then I rode it for about five and then shut it off. Also the valves weren't too tight they were too loose

 

[buckeye]

Then readjust them.

 

[Txpowdercoater]

Never had one apart. Is it possible that with the valves misadjusted the piston hit a valve and damaged it?

nope, his issue would be and is most likely caused by valve lash waaay to loose. I'm betting the cam compression release is doing its job, its just way out of adjustment on the valve lash.
should set intake to .002 and exhaust to .003

edit: I see its having running issues now. set the valves correctly, if they are to tight, when the engine is warmed (5 minutes of riding you did) metal expands and they are probably holding the valves just off of their seats a slight bit....when cooled runs better, that means should adjust valves again to the specs I listed above. make sure the lock nut does not change the gap. I leave the blade in and tighten carefully, its very easy to change lash during tightening stage.

 

[Stephen115]

nope, his issue would be and is most likely caused by valve lash waaay to loose. I'm betting the cam compression release is doing its job, its just way out of adjustment on the valve lash.
should set intake to .002 and exhaust to .003

edit: I see its having running issues now. set the valves correctly, if they are to tight, when the engine is warmed (5 minutes of riding you did) metal expands and they are probably holding the valves just off of their seats a slight bit....when cooled runs better, that means should adjust valves again to the specs I listed above. make sure the lock nut does not change the gap. I leave the blade in and tighten carefully, its very easy to change lash during tightening stage.

Thats what I've been doing, I agree with you on the metal expanding. The cam card said .003 on both sides but I think I'll set the intake to .002 like you said. I noticed once it cooled down it would start right up.

Thanks

 

[Txpowdercoater]

Thats what I've been doing, I agree with you on the metal expanding. The cam card said .003 on both sides but I think I'll set the intake to .002 like you said. I noticed once it cooled down it would start right up.

Thanks

just check them both again and make sure your very careful during tightening (both tension nut and locknut, its easy to move both while doing this), its always something I have to carefully watch and constantly sliding the feeler blade back and forth while I tighten making sure it doesnt take more effort to slide it and move it which means its making a dimple in the thin blade and henceforth be out of adjustment. .002 and .003 is veeeeery damn thin! easy to be off during the locknut part of the job.

 

[Stephen115]

just check them both again and make sure your very careful during tightening (both tension nut and locknut, its easy to move both while doing this), its always something I have to carefully watch and constantly sliding the feeler blade back and forth while I tighten making sure it doesnt take more effort to slide it and move it which means its making a dimple in the thin blade and henceforth be out of adjustment. .002 and .003 is veeeeery damn thin! easy to be off during the locknut part of the job.

thanks :thumbsup:

 

[youngengines]

Actually, when the engine warms up the valve lash opens up. Thats why on a race engine, most set the lash as close to zero as possible cold.

 

[Txpowdercoater]

Actually, when the engine warms up the valve lash opens up. Thats why on a race engine, most set the lash as close to zero as possible cold.

this I would have to be shown to believe it, sorry. metal expansion is ever so slight of course, but it does happen with heat.
When all metals heat up, they expand, one would think that equals the rocker tips, valve stem tips, lifters, etc etc, all of this warming up and expanding equals fatter parts so to speak...how would that make the gap larger?
not trying to be a butt, but that goes against anything I was taught with all motors and such for the last 50 years.
to install bearing races in cases, I freeze the race and heat or warm the case, the race drops right in and when the temp equal to ambient, metal shrinks to grab the race tight. different metals expand at different rates with different heat.

 

[youngengines]

this I would have to be shown to believe it, sorry. metal expansion is ever so slight of course, but it does happen with heat.
When all metals heat up, they expand, one would think that equals the rocker tips, valve stem tips, lifters, etc etc, all of this warming up and expanding equals fatter parts so to speak...how would that make the gap larger?
not trying to be a butt, but that goes against anything I was taught with all motors and such for the last 50 years.
to install bearing races in cases, I freeze the race and heat or warm the case, the race drops right in and when the temp equal to ambient, metal shrinks to grab the race tight. different metals expand at different rates with different heat.

I have a 406ci engine with aluminum SB2.2 heads in my Vega street/strip car. I set the valves at .008 cold and when hot they are .018 to .020. I set the kart engines as close to zero as possible when cold and when hot they are much looser, I just havent actually checked them with a feeler guage to see how much. I have been building engines for all my adult life (I am 45), so this I know about. I have saw "tight lash" late model stock cams (circle track) cars that when cold would actually "pop" from the valves not totally seating on a cold day when firing up to put some heat in them before hot laps. Not trying to be rude, just sharing my personal experiences.

 

[minibikin']

Actually, when the engine warms up the valve lash opens up. Thats why on a race engine, most set the lash as close to zero as possible cold.

Coming from the Aircooled VW world this is oh so true.

 

[texasfabguy]

It's the aluminum head expanding more than the steel.

 

[Txpowdercoater]

I have a 406ci engine with aluminum SB2.2 heads in my Vega street/strip car. I set the valves at .008 cold and when hot they are .018 to .020. I set the kart engines as close to zero as possible when cold and when hot they are much looser, I just havent actually checked them with a feeler guage to see how much. I have been building engines for all my adult life (I am 45), so this I know about. I have saw "tight lash" late model stock cams (circle track) cars that when cold would actually "pop" from the valves not totally seating on a cold day when firing up to put some heat in them before hot laps. Not trying to be rude, just sharing my personal experiences.

now see, I've never checked mine hot, I will indeed on my small motor and see if I am losing lots of cam instead of it being where it should be. now I am gonna have to goof with it and see whats really happening cold and hot...
btw, I checked via google on you, I will indeed listen to ya

 

[youngengines]

now see, I've never checked mine hot, I will indeed on my small motor and see if I am losing lots of cam instead of it being where it should be. now I am gonna have to goof with it and see whats really happening cold and hot...
btw, I checked via google on you, I will indeed listen to ya

I dont blame you for checking up on me, the internet is full of crap sometimes isnt it? Good luck to you in your testing and have a Merry Christmas!