Pull Start Locks with Spark Plug Installed - HELP!

Ok, so I installed my new spark plug after doing my run through of installing new mods on my cag. I go to pull the pull starter to test it and it seems VERY HARD. It locks up at about half a pull yet if you pull very slowly it will pull somewhat easy.

I took off the spark plug and then tried to pull it again and it pulled perfect, as easy as it was when I first got it. So I put the stock plug back on and it does the same thing as with my HP plug.

Basically its impossible to pull start with a plug installed and easy without a plug installed yet of course the engine wont start without a plug.

Anyone know what to do?

What mods did you do?

IP2 Exhaust with rewelded silencer, 3mm reed spacer, ada billet filter, cf reeds, and triple tappered needle at the 3rd setting

compression from the piston and head its normal to do that wit the plugs on but when off it blows air out. give it sum more oil and prime it

Of course it's compression but with the few mods I made how would it triple the compression almost? It feels around 8 times harder to start. I can only pull the cord out 1/4 of the way before the bike jumps with it.

wats ur gas/oil mixture?

Is your plug longer than the old one? The piston may be topping out on it.

Start backing the plug out until the motor turns over. Is the new plug the same exact model as the old one? I bet that you may be running the wrong plug by mistake.

he did put back his stock plug mayb the stock plug is fouled

Check your cf reeds and spacer.Maybe something is cocked and not leting you reeds to work right.or the reeds are too big not leting them move.

Only 2 things causeing this... Either your pluyg is too long and is hitting the top of your piston, or its just a matter of really high compression.

The only time I have seen compression so high that the pull starter was hard as hell to pull was on a Cag that had a TS head (Trevor Sellers) with adjustable domes. I mean this thing was hard as hell to pull. You had to kneel over the seat just to keep the bike from lifting off the gound!!!

Other then that, I dont know *** it could be???

Do you have the stroker crank in your bike? I see you have it in your avatar. If you do, did you set the squish?

as well as crankcase clearance?

If the spark plug is hitting the piston on the top,add the spacers from the stock plug. Because it may just be alittle off and it won't start. Or the compression is to high.

Well after many hours of experimenting I found the problem and as many of you said it was the plug hitting the piston. The new plug is slightly longer than the stock and therefore it was hitting. I took the spacer off the stock and placed it on the hp plug and I found it still was not long enough. Still hitting by about 2 turns out.

So I found a thick rubber oring in my shop that fit snug around the plug and that did the trick. I tightened it down and its all set. Even though I still dont have my clutch, housing or chain in I am going to start her up in about an hour to make sure it runs all good.

Thanks for all of your help!

One last question, thoughtout the testing I pulled the pull starter many many many times and since the piston was infact hitting the plug did that damage the piston?

Thanks again, I'm off to buy some gas.

Arrghh, don't start it, go and get a proper plug, or use your old plug. The head temps go above 400 degrees the o-ring will probably melt, either the plug will be blown out taking the thread with it or it will take out the top of the piston. Go to any place that has a plug book and get the same heat range plug of your new one with the retracted style of the old one.


Man, dont let a $2 part fark your entire motor.

Exactly!!! A plug is not gonna give you a dramatic difference in performance. I run a NGK bmp7a or a bm7a. These are $3 - $5 bucks and work well.

yea man dont you know o rings are just gunna melt when you heat it up? get a proper plug there not going to make a difference besides temp really and the top of the piston might have a sctrach on top of it but its all filled with carbon and doesnt even matter

Lastly... if you start using all those rings and spacers I know for sure you will not get a good seal and you will lose compression BIG time!

Are you sure the plug isn't hitting the piston. AsNGK race plugs b8-9 egv wont fit in my Chilini engine without fouling the piston. Something to check out anyway mate.