Makita 4 Cycle Trimmer - any mechanics on here?

Joined
Dec 2, 2016
Messages
74
Location
Midwest
Hey small engine shade tree mechanics and professionals -
I have a 2.5 year old Makita trimmer with low hours - maybe 10. Its a 4 cycle, separate gas/oil, not a 4-mix. This year it developed a problem where it became hard to restart hot and if i got it going, it would idle out and die. When cold, it starts first pull, it idles well when cold and has amazing power. If i shut it off for 15-20 min, restarting is only made by holding down the throttle and pulling. If i get it going then, it will then idle out. Things I have done so far:

1. Adjusted idle screw - I have a tachometer
2. Adjusted/checked valve lash - they are perfect
3. Spark arrester was removed day one of ownership
4. Oil is clean
5. Air filters are clean
6. Carb body and related gaskets appear tight and clean
7. I metered resistance of coil its within spec. I have not done this when its hot, will this make a difference?
8. Thought it was venting problem, removing gas gap - no improvement
9. Took it to local mechanic, who said it was idle screw wiggling and getting out of adjustment, so I put some loctite on the screw to hold it down. I used low strength locktite, but it made no difference for hot restart problems.
10. NEw spark plug with correct gap made no difference.

I'm at a loss for what it could be. I'm close to buying a new carb, but they are like $50 and I really don't think its the carb. The carb is not adjustable since its a 4 cycle. Any other suggestions for me? I love this trimmer, but its giving me a headache with this problem. This is a professional model and cost about $300 new, so i'd like to fix it.

Any ideas? Thanks so much
 
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Man, you've done some excellent diagnostic work there and have covered a lot of possibilities. Many years ago I did have a situation where the coil acted up only when warm. This article talks about it some: http://www.your-lawn-care-basics-coach.com/Lawn-Mower-wont-start-when-hot.html

It sure seems to be temperature related. Is a carb kit available...they tend to be very inexpensive. Fuel line and filter are good?

Hopefully someone else with more experience will chime in.
 
Check if there is any air leak between carburetor and cylinder...spray wd40 in between when it will be running...if engine will quit...then it is gasket...
 
Any chance it is running on winter fuel?

Years ago I came home on a unusually warm spring day to find all my gas cans looking like weeble-wobbles in my garage from all the butane trying to return to the atmosphere and bloating the gas cans from the vapor pressure. You can get vapor lock with winter fuel in summer stuff, so I dump it all before mowing season starts.
 
Like doitmyself, I would guess it might be ignition coil. I once had a 2-cycle Homelite hedge trimmer that would start and run well when cold, but once it was warm it was almost impossible to get restarted. I don't remember it dying while running, but if you shut it off, or ran it out of fuel, much of the time it had to cool off before it would restart.
I eventually swapped another ignition coil on the engine, and the hot start problem went away. You might check with your dealer. Sometimes manufacturers have a longer warranty on the ignition system.
Good luck getting it running well again.
 
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Originally Posted By: Kamele0N
Check if there is any air leak between carburetor and cylinder...spray wd40 in between when it will be running...if engine will quit...then it is gasket...


Thanks ill try that
 
Originally Posted By: MichiganMadMan
Any chance it is running on winter fuel?

Years ago I came home on a unusually warm spring day to find all my gas cans looking like weeble-wobbles in my garage from all the butane trying to return to the atmosphere and bloating the gas cans from the vapor pressure. You can get vapor lock with winter fuel in summer stuff, so I dump it all before mowing season starts.


Fuel was pumped in April 2017, I always mix stabil with fresh fuel when its pumped.
 
T
Originally Posted By: m21bmr
Like doitmyself, I would guess it might be ignition coil. I once had a 2-cycle Homelite hedge trimmer that would start and run well when cold, but once it was warm it was almost impossible to get restarted. I don't remember it dying while running, but if you shut it off, or ran it out of fuel, much of the time it had to cool off before it would restart.
I eventually swapped another ignition coil on the engine, and the hot start problem went away. You might check with your dealer. Sometimes manufacturers have a longer warranty on the ignition system.
Good luck getting it running well again.


Thanks. I might meter the coil when warm to see what resistance it has. The normal warranty is only 2 years, but your right for the coil it might be longer...
 
I have a 2 cycle lawnboy mower that when the coil starts getting weak will do as your Makita. I have replaced the coil now 3 times since I bought it in 2003
 
Originally Posted By: bioburner
I have a 2 cycle lawnboy mower that when the coil starts getting weak will do as your Makita. I have replaced the coil now 3 times since I bought it in 2003
lol just delivered in my hands today coil for my lawn boy it's on its 3rd one quick simple job at least.
 
Originally Posted By: meep
what are the chances it's running rich/flooded on hot restart?


Its possible, however, since the carb is not adjustable there is no way for me to test this. I looked at coils, they are surprisingly cheap for this unit, around $15.00 I thought they would be like $40-50. I'm either going to replace the carb or the coil. I might start with the coil replacement since that is going to be cheaper. Is possible i need to adjust the needle in the carb. I might check that prior to ordering a coil. Seems odd that it would only flood when warmed up? I would think it would flood it right away, but it runs fine on cold starts...
 
Originally Posted By: Rab6715
Originally Posted By: MichiganMadMan
Any chance it is running on winter fuel?

Years ago I came home on a unusually warm spring day to find all my gas cans looking like weeble-wobbles in my garage from all the butane trying to return to the atmosphere and bloating the gas cans from the vapor pressure. You can get vapor lock with winter fuel in summer stuff, so I dump it all before mowing season starts.


Fuel was pumped in April 2017, I always mix stabil with fresh fuel when its pumped.


April is still in the change from winter to summer fuel in the Midwest. I doubt it is your problem but just an FYI.
 
Update -

Ordered a $15 coil from Makita. Same result. I'm coninvced now that it has to be carb related. New carb is only $30. I guess I spent to much money on this trimmer to retire it already
smile.gif
. New carb should be here in a couple weeks. Crossing my fingers this is the problem.
 
I have a 4 cycle ryobi trimmer that does the same thing. Runs great when you first start it up, don't even have to choke it...it'll start first pull every time. I'll cut about half of my ditch, or if I'm using the edger attachment I can do one side of the drive way, then when it gets hot it just stops. It's almost like it locks up, but you can still pull the cord, but it'll never restart until it cools off. Let us know what you find out.
 
What happens if you unscrew gas screw? Sounds like that you have vapour lock.....

Also try to get rid off that mesh/screen in your muffler.....to help cool down the engine
 
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