Guys...I need your help!!!!!!!!!

runnermike · Aug 15, 2014

My motor will not start! It's a HF 79cc. It's the same motor I had on my previous build. It started every single time on first or second pull! It's still a fairly new motor.

Since my last build....here is what has been done to the motor
-18lb valve springs
-set valve lash
-set coil gap to .021

Motor has oil and carb is getting fuel. It will not turn over. I believe it's getting compression because I can feel air coming out of the exhaust. It just won't fire like it's not getting spark.

I removed the spark plug and tried cranking to see if I had spark.....I saw nothing! Out of the many many times I tried...I only felt a slight tingle once! At the base of the spark plug wire it looks a tad dry rot, but nothing major.

Am I missing something? I feel completely lost!!! I have attached a pic of the coil. Magnets on the flywheel are good as well.....

The gas I put in is fresh, but the carb is not brand new. It is the one from my previous build, but still fairly new. It's the 19mm v slide carb. When I removed it from my last build I drained it so no gas would sit in it and go stale.

Could something be out of whack inside the engine? I did have the side cover off so I could drill and tap it....uggghhhhh I'm going nuts!

Thanks,

Down and out an frustrated Mike

F_Rod81 · Aug 15, 2014

Take off your valve cover and attempt to pull start it. Can you see the valves activating?? If you don't see them moving up and down then you'll need to start the valve job over.

Did you line up the timing marks when you installed the valve springs? If you just installed the springs and set the lash that could be your issue. Coil gap is okay. If the CDI when out then that will be the first time I've heard of it with these engines.

I'd say start over from step one. . .

- Take off the side cover
- make sure the timing marks are lined up
- make sure the tappets' are on the camshaft
- make sure the push rods are seated in the tappets'
- once these are confirmed, then set valve lash without the side cover on so you know the timing marks don't move.

runnermike · Aug 15, 2014

Frank....I will do that. I did make sure the timing marks were lined up though. Tappets???

Here's one thing....when I put the palm of my hand over the exhaust and cranked...it popped like it wanted to start and it was hot! Whereas before just putting my hand by it and cranking I could just feel air.....?????????

runnermike · Aug 15, 2014

The marks are lined up correct?

runnermike · Aug 15, 2014

The valves move up and down. Push rods are seated. I figured out what the Tappets are and the are touching the cam shaft. When I slowly pulled the pull starter I could here the intake sucking.....

I'm just frustrated.....

F_Rod81 · Aug 15, 2014

If everything appears to be good inside the engine then start diagnosing outside the engine. Do a leak down test to see if there is any air leaks. Maybe your idle is set too low or air/fuel ratio set too lean. Check the plug wire to see if there are any cuts or tears, although it may look minute, its possible to sever the inside wire.

runnermike · Aug 15, 2014

Well....after cleaning the carb and making sure the gas is good and checking for leaks....all places where there are gaskets have no leaks....still will not crank! It is just acting like there is no spark/fire.....I'm lost and frustrated....I'm calling it a night :-(

dmb · Aug 16, 2014

take the coil off and sand the bottom till its nice and clean then do the same to the flywheel. wipe with cleaner then re -install do not hook-up the kill switch. pull starting should blow your thumb off the hole and shock you pretty good if you hold the wire. good luck. dennis

maniac57 · Aug 16, 2014

Bad coil or something assembled incorrectly causing no spark.
Check the crank key? Magneto? Plug? Wire?

curtisfox · Aug 16, 2014

To me it sounds like the coil gap is to much. What we have been doing for years is use a 3x5" recipe card ( or match book cover) put that in between the magnets and coil tighten it up, rotate the fly wheel till the card comes out and you should be good to go. Have been doing it for years works every time. I think they are .019................Curt

Bruce Lee · Aug 16, 2014

I have had two of these engines come from the factory with no continuity from coil to plug. Found that the plug wire into the coil missed the screw point in the coil. I strippede off and exposed about an 1/8 inch of conductor, screwed in the plug wire. Wham first pull started and ran good.

runnermike · Aug 17, 2014

Ok guys....I reset the coil gap and sanded the magnet and bottom of coil. Removed the spark plug, hooked it to the wire, held it in my hand, and pulled the pull starter....IT LIT ME UP! I have spark but....still won't crank!

I went through everything again. Timing marks are lined up. Push rods are in the Tappets. Valve lash is set. Nothing seems or looks damaged. Brand new fuel too. The only thing that is not factory is my gasket between the intake manifold and head. I made one out of gasket material from the auto parts store since I lost the one from AGK.

I have a very short header on the exhaust since mine is not done yet. Could this be a problem?

I just feel completely lost here! This is the same engine that started every single time on my previous build.

Can you guys think of anything?? I'm REAL close to just purchasing another engine!

:-(

runnermike · Aug 17, 2014

Ok guys....I reset the coil gap and sanded the magnet and bottom of coil. Removed the spark plug, hooked it to the wire, held it in my hand, and pulled the pull starter....IT LIT ME UP! I have spark but....still won't crank!

I went through everything again. Timing marks are lined up. Push rods are in the Tappets. Valve lash is set. Nothing seems or looks damaged. Brand new fuel too. The only thing that is not factory is my gasket between the intake manifold and head. I made one out of gasket material from the auto parts store since I lost the one from AGK.

I have a very short header on the exhaust since mine is not done yet. Could this be a problem?

I just feel completely lost here! This is the same engine that started every single time on my previous build.

Can you guys think of anything?? I'm REAL close to just purchasing another engine!

:-(

Greg58 · Aug 17, 2014

Mike what does the spark plug look like right after you try to start it? If its dry you may not be getting fuel through the carb, I'd try a little starting fluid to see if it will bump at all. If it doesn't hit on starting fluid you have to have a bad coil or plug.

runnermike · Aug 18, 2014

After taking Greg58's advice, I sprayed some starting fluid in the carb. After a couple pulls, it sounded like it wanted to start. What should I look for in the carb? Could it be dirty or clogged? I have the 19mm v slide carb from AGK....

I'm starting to think this might be a fuel/carb issue....

runnermike · Aug 18, 2014

I took the carb apart and thoroughly cleaned..although it looked pretty good. Tried starting again but no luck. It only popped once! I pulled the spark plug and it was not dry...its getting fuel. So, new spark plug, coil???

I'm about ready to call it quits..... :-(

MotoMagz · Aug 18, 2014

Don't quit ..you will get it. You are getting close.!

runnermike · Aug 18, 2014

I just don't know where to go from here...? Short of purchasing a new carb, spark plug, and coil...I'm lost! I don't even know where to get a spark plug. Hopefully someone will know who carries a replacement. I'm pretty sure they don't sell replacement coils so I doubt I can even find one....UGH!

runnermike · Aug 18, 2014

http://custommotoredbicycles.com/ez...parts/more_4_stroke_parts_79cc_harbor_freight

Is this the right spark plug? I found a coil on ebay....probably gonna order it tomorrow.

Greg58 · Aug 18, 2014

Mike a #5 is pretty hot, the one shown is a extended tip resistor but a b6hs like we run in the two strokes can be found at just about any parts store.

Guys...I need your help!!!!!!!!!

Member

Dealer

Member

Member

Member

Dealer

Member

Active Member

Old, Fat, and still faster than you

Well-Known Member

New Member

Member

Member

Well-Known Member

Member

Member

Well-Known Member

Member

Member

Well-Known Member