engine hard to spin, feels like its binding

[Davidgx200]

I have a 6.5 clone, my setup is governor removed, 18lbs springs, gx140 emulsion tube,88 main jet, drilled low speed jet, k&n air filter and billet adapter, custom header, arc billet flywheel, 4degree offset timing key, arc billet rod 0.020" longer than stock, honda flat top piston and autolite ar3910 plug. Everything ran good as of saturday. I wanted to do more like always had my head shaved 0.045" , ported and polished. turned my huayi carb into a stock appearing carb venturi bored to 0.690" shaved throttle shaft and butterfly screw, 91.5 jet, emulsion tube drilled out and tip shaved to sit lower in the floor of the carb. when putting everything together i spun the engine to check clearance and interference. everything looked good. when trying to pull start it the rope stop and jerked me. I took the side cover off and hand turned it. One rotation was smooth the next was hard, so I took the head off and no marks of anything hitting compression release on cam seems to be fine. set valve lash over and over also. Turning with the head off was easy til I put pressure on the pushrods with my other hand then one turn easy the other stiff and real hard to spin. Sorry for writing so much but can anyone help me with this? Also is there a timing key chart or guide for mods or is it all trial and error? Anyone got a suggestion on offset timing key for this high compression setup? Thanks in advance.

 

[Brandon1023]

Have you checked your coil? Just a thought. Maybe the coil is attracting the magnet on the flywheel which is causing the resistance you're describing.

 

[Davidgx200]

I haven't checked it since putting everything back together but I'll look at it after work today and post back

 

[Davidgx200]

The only weird thing is with the head off while spinning it, its very easy til I put pressure on the pushrods by hand then every other rotation I strain to spin the crank by hand

 

[Brandon1023]

If not the coil, I'd remove the "OHV Cover" and check the rockers as a second idea.

 

[r_chez_08]

Is it not just the natural compression of the compression stroke?

 

[KieranM]

Is it not just the natural compression of the compression stroke?

That is what I'm thinking, you have done a lot to the engine.

 

[OzFab]

If not the coil, I'd remove the "OHV Cover" and check the rockers as a second idea.

Is it not just the natural compression of the compression stroke?

Sorry guys, but go back & read it again: with the head off, it still happens when pressure is applied to the pushrods.

With the head off, you turn the crank, what happens to the pushrods? Do they rise & then fall or stay up? Reason I ask is I'm thinking it may be a lifter problem; maybe something stuck in the guide or even a bent lifter. This will definitely "bind up" the engine.

 

[Bluethunder3320]

maybe with the longer rod the piston is hitting the head?

does it turn over smooth with the head on and the push rods not in it?

 

[Davidgx200]

great idea Brandon1023 the coil had come loose and worked itself to the flywheel and it had a strong pull on the magnet. Thanks for all the suggestions guys. Good attention to details earlier fabroman. Heres the new problem I gapped the coil at 0.020" and it still get stiff while pulling but not like before. It doesn't want to fire up it has backfired once or twice when it did start it idled fine but when you give it gas it stalls out. Thinking of gapping coil a little more still cant pull without hurting yourself or tiring yourself out. Is it timing? I only have a stock key 4 degrees, and 8 degrees offset timing key. I'm running 4 degrees advance right now. Any suggestions?

 

[Davidgx200]

AGK said set gap at 0.020" I went to ARC and the flywheel I have says set coil air gap at 0.030"

 

[Doc Sprocket]

That's wild... I have always set my gaps at 0.010". Honestly, I can't see the mag gap having anything to do with this.

 

[OzFab]

If you've increased your compressoin ratio (by shaving the head/block or longer rod/piston) it will be harder to pull

 

[Doc Sprocket]

If you've increased your compressoin ratio (by shaving the head/block or longer rod/piston) it will be harder to pull

That was my first thought, but seemed to be too obvious. Also- although valve lash has apparently been reset to spec, I wonder if something is negating the effectiveness of the compression relief mechanism? FTR, one thing that will decrease the effectiveness of the mechanism is excessive intake valve lash.

 

[Davidgx200]

I was thinking of what could cause the compression release on the cam to not work properly. I set valve lash at 0.002" intake and 0.003" exhaust. no its definitely the compression the coil hurt me when it came loose and setting against the flywheel. Anybody setting valve lash differently?

 

[Davidgx200]

I read others are pull starting as high as 14.1 compression on minibike with no problem, as long as the compression release is work well.

 

[Brandon1023]

Honestly, I have changed 2 ignition coils on mowers so far, and readjusted plenty, and all I do to set it is eyeball it with a card just thick enough to fill the gap, then tighten it and check for spark. Works every time for me. I don't own any gap spacer things.

 

[Doc Sprocket]

Honestly, I have changed 2 ignition coils on mowers so far, and readjusted plenty, and all I do to set it is eyeball it with a card just thick enough to fill the gap, then tighten it and check for spark. Works every time for me. I don't own any gap spacer things.

Most standard business cards are around 0.010". That's the "gauge" I tend to use. Loosen the mag, stick the card in, let the magnet pull it tight, snug up the bolts, pull the card out. Done!

 

[slideways]

You do have to run extra gap on an ARC flywheel. The magnet is so much stronger and also the fact that aluminum "grows" a tick at a high rpm and is more subject to heating and expansion. Set the gap where ARC says to set it.

Your backfire is probably carb or valve lash related. The only other thing to try is to put a straight up key in the ARC wheel to eliminate that as a problem. The ARC wheels usually have a little bit of timing advance built into them already.

 

[r_chez_08]

The keyway is fixed in the stock position and the stock pull starter can be used.

I am stumped.
Do you have another cam and the stock head you can try?