chry 7.5hp issues

[spinelli006]

Ok I rebuilt my Chrysler 7.5hp its a 79 72h9b motor during the rebuild it got new crank seals and the head and block machined due to it being warped and new head gasket put it all together and now it only runs 2/3 to full throttle carb is clean and so on I hope u guys have a idea willing to try anything I'm running 93 oct with ams oil in it around 50:1 40:1 and plugs after I run it are a light brown off white I wanna say a little lean but don't think its a issue I add a touch of fuel and it chokes

Well hope my info helps I'll answer questions the best I can

 

[MickLovin]

Re: chry 7.5hp issues

When it runs 2/3 to full does it pump water ok, as you mentioned your plugs were white?

Have you got the right plugs in and gapped correctly and are your points clean and gapped correctly?

Have you tuned your low idle speed? If it is white on the plugs, it does sound to lean try screwing in your air mixture to lightly seated then out again 1 Full turn and a 1/4 turn, seen people do half a turn thinking it is a full turn. There is also a youtube video on how to set your idle for a 9.9hp chrysler i think. check that out or refer your manual.

 

[spinelli006]

Re: chry 7.5hp issues

When it runs 2/3 to full does it pump water ok, as you mentioned your plugs were white?


Yes it pumps water fine the plugs are closer to a light brown


Have you got the right plugs in and gapped correctly and are your points clean and gapped correctly?

Well I have replaced the plugs a few times I just got the same ones that were in it before that it ran fine on last season and this model has a coil set up



Have you tuned your low idle speed? If it is white on the plugs, it does sound to lean try screwing in your air mixture to lightly seated then out again 1 Full turn and a 1/4 turn, seen people do half a turn thinking it is a full turn.

Yes I messed with that when I had it running*it helped but not enough to make it idle

Last season it ran ok somewhat idled and didn't run this bad some I'm not sure if I messed up something or what

 

[spinelli006]

Re: chry 7.5hp issues

Well checked spark today everything looks good there and fixed a fuel line still no good news . I'm gonna check compression tommarrow make sure my new head gasket is sealing good and maybe go threw the carb again

 

[spinelli006]

Re: chry 7.5hp issues

Well been thinking a lot about it and a comment from someone so it doesn't run with the choke on at all sorta points towardsiitsgetting to much fuel iI think I'm gonna go threw the carb again

 

[Frank Acampora]

Re: chry 7.5hp issues

When reassembling, you must synchronize the carb opening to the timing. There is a mark on the advance plate where the carb roller should contact the plate as you advance the throttle. The carb also has an adjustment to set the butterfly opening at idle. Correct setting of this will determine whether or not the engine will run at idle.

Do not use high octane or premium fuel unless the head and block have been milled so far that compression is above 145 PSI--test it!

 

[MickLovin]

Re: chry 7.5hp issues

I'm trying Master Frank

 

[spinelli006]

Re: chry 7.5hp issues

Ok thanks I will try those And I will try and test compression today and see where I'm at with that

 

[spinelli006]

Re: chry 7.5hp issues

Also any tips on adjusting the butterfly for idle ?

 

[Frank Acampora]

Re: chry 7.5hp issues

It varies from engine to engine and carb type. Basically, on the metal carb linkage, with the carb butterfly fully closed, you set the roller on the scribed line OR other spot designated in the manual. then you start the engine and warm it up. As you lower the speed with the tiller you adjust the screw on the carb until the engine will idle smoothly without stalling. I forget exactly how the plastic linkage is set, but if the adjusting screw has been set in too far and broken the plastic you will need another link.

Obviously, before you do this you double check that points are clean and gapped correctly and plugs are clean and firing.

 

[spinelli006]

Re: chry 7.5hp issues

Check compression I have around 145 on top and 140 on bottom

 

[spinelli006]

Re: chry 7.5hp issues

What oil mix should I be running on a 1979 Chrysler 7.5hp

 

[MickLovin]

Re: chry 7.5hp issues

mine is a 6hp and 12.9hp and both run on 50:1

 

[spinelli006]

Re: chry 7.5hp issues

Ok cool so running the motor this weekend and runs better with choke a little pulled think I need a bigger main jet ?

 

[MickLovin]

Re: chry 7.5hp issues

No more likely you need to adjust your carbie setting on the screw on the metal adjusting section attached to your carbie.