Homelite 750 score,but no spark :(

[hoss]

You're not grounding out somewhere between the coil and the tramsformer are you? Have you established for sure that this IS a spark issue? Thanks for keepin us in the loop. I am always ready to learn somthing new about these saws.

 

[lesorubcheek]

Did ya also try changing out the trigger module, or did you just try swapping the transformer? The transformer can be checked with an meter, but don't know any way to test a trigger module other than by seeing if it'll give a spark when connected in the "system".

As Hoss suggested, grounding may be an issue. May want to verify the left side of the transformer receptacle has a good ground contact. This is a point that Raised By Wolves brought up earlier, and its a good thing to check out.

Dan

 

[roncoinc]

You're not grounding out somewhere between the coil and the tramsformer are you? Have you established for sure that this IS a spark issue? Thanks for keepin us in the loop. I am always ready to learn somthing new about these saws.

I pulled the starter off and the previouse owner had unhooked and taped the end of the wire to the on/off switch..
i checked the length of that and of the wire to the transformer..
the gap on the wheel looked kinda large but the pickup was still mounted solid and didnt move so i figured after all these years it must be correct..
i also check for continuity from the hot side of the transformer contact to ground and that was good also..
put mix down the carb and pulled,and pulled and now my arm is sore and not once did it even give a hint of fire..
the test setup showed no spark even from the transformer off the running saw,put it on and mounted it to try anyway..
what next ??

 

[hoss]

I pulled the starter off and the previouse owner had unhooked and taped the end of the wire to the on/off switch..
i checked the length of that and of the wire to the transformer..
the gap on the wheel looked kinda large but the pickup was still mounted solid and didnt move so i figured after all these years it must be correct..
i also check for continuity from the hot side of the transformer contact to ground and that was good also..
put mix down the carb and pulled,and pulled and now my arm is sore and not once did it even give a hint of fire..
the test setup showed no spark even from the transformer off the running saw,put it on and mounted it to try anyway..
what next ??

Take a piece of note book paper, fold it in half and insert both layers between the coil and the flywheel, rotate the flywheel until the magnets are opposed to the coil leads, then loosen the retaining bolts on the coil, let the coil draw up tight against the magnets with the two layers of paper in between then re-tighten. Reassemble and try to start. If this also does not work then maybe it is just a bad coil. Man! This one is a head scratcher.

 

[lesorubcheek]

I agree with Hoss. Wouldn't assume the gap is correct. If its too wide, this could be the sole problem.

Dan

 

[roncoinc]

Notebook paper ? like regular paper in my printer ?? how about the usuall biz card ??

Did ya also try changing out the trigger module, or did you just try swapping the transformer? The transformer can be checked with an meter, but don't know any way to test a trigger module other than by seeing if it'll give a spark when connected in the "system".

How do you check the txformer with a meter ?? continuity from hot to ground ?? spring thing in the middle i guess would need to be in the circuit and look for loss in between ?? i dont have a VTVM anymore,only a fluke..

will the module from the saw i took the txformer off fit ??

tnx guys..

 

[lawnmowertech37]

Did ya also try changing out the trigger module, or did you just try swapping the transformer? The transformer can be checked with an meter, but don't know any way to test a trigger module other than by seeing if it'll give a spark when connected in the "system".

As Hoss suggested, grounding may be an issue. May want to verify the left side of the transformer receptacle has a good ground contact. This is a point that Raised By Wolves brought up earlier, and its a good thing to check out.

Dan

dan you talking about this ?

http://www.cmsmallengines.net/homelite-receptacle-a70088.html

 

[hoss]

Notebook paper ? like regular paper in my printer ?? how about the usuall biz card ??

Printer paper, legal pad, either way will work. Sometimes a buisness card can be too thick plus not being as flexible as the paper it can keep the coil leads and magnets from proper mating position.

 

[lesorubcheek]

Here's some typical readings from a transformer. Wish I knew a way to measure and test the trigger module, but unfortunately I don't.

Maybe this will help at least eliminate the transformer.

Dan

 

[roncoinc]

Here's some typical readings from a transformer. Wish I knew a way to measure and test the trigger module, but unfortunately I don't.

Maybe this will help at least eliminate the transformer.

Dan

Wow man,tnx,awsome effort on your part !!

used my fluke "83" and checked the two that are off and close enough to your readings..
will set gap like Hoss said anyway and see what happens..
so will the module interchange from the other saw ?? i think a 330 ??
i can take it apart tomorrow and see i guess..
thanks again for all the effort..

 

[lesorubcheek]

BTW, the flywheel to trigger module gap according to the "book" is 0.015".

Dan

 

[lesorubcheek]

350, 360, 550, 650 and 750 all used the identical trigger module and transformer. The 450 from factory had a "blue" module which was rev-limited to work in conjunction with the fixed hi-jet carb. It'd work though to at least check for spark. They do get swapped out, so 450s can have the black one's in 'em too of course.

330's have a one piece module assembly, so its very different.

Dan

 

[leeha]

What i have done in the past especially
with these Homelites with this ignition is
swap out each individual component one
at a time with a known good one and see
if you have spark or if it will start. i have done
the testing with meters and thought parts were
good only to find out you had one bad one.

Like Dan and Hoss said' make sure all gaps and
grounds are good.


Lee

 

[Mastermind]

Nice score Ron, cool of you guys to help figure this out. I'm looking forward to seeing this beast in some big wood.

 

[roncoinc]

It was the module !!
took the one out of my 360 and fired on second pull !!
anybody have a module i can put in the 360 to get that back together ??
thank you very much all of you for the help !!
finish it up later today and make a video

 

[hoss]

Sounds good. I'm lookin forward to it.

 

[ronT2]

Man! great score!
People at the last gtg compaired mine to a cinder block with handles...until they ran it!

Jim, that is one kick @$$ fun saw to run. It cut alot smoother than I thought it would.

roncoinc, glad you got it running. If you haven't run one before I can't wait for your first impressions.

 

[lesorubcheek]

That's great news you found the problem Ron. There's 3 or 4 of each of the '50s sitting around here, and its funny that none of 'em have bad modules or transformers, at least in their electronics. Had a spring inside the transformer break on a couple, but that's it. The only other problems with 'em has been related to a poor contact, usually on the grounding at the receptacle.

Dan

 

[leeha]

Congradulations, Glad you got it
figured out and running.


Lee

 

[hoss]

It was the module !!
took the one out of my 360 and fired on second pull !!
anybody have a module i can put in the 360 to get that back together ??
thank you very much all of you for the help !!
finish it up later today and make a video

These things turn a lot of revs for a big saw (12,500) so make sure your rakers aren't too low and be sure that the auto oiler is pumping well. The auto oilers work great when they work, but need to be maintained as they don't have a lot of tolerance for dirt in the lines or worn O-Rings on the pump body.