Makita 4 Cycle Trimmer - any mechanics on here?

Originally Posted By: Kamele0N
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


The spark Arrestor has been removed already and I've tried unscrewing the gas cap, same result.
 
try some fresh ethanol free fuel? Maybe splurge one one of those little cans ethanol free 90octane.

Sounds like vaporlock to me. Not sure why it would be a carb if it starts and runs fine cold..

Truely a puzzle
 
Originally Posted By: Rand
try some fresh ethanol free fuel? Maybe splurge one one of those little cans ethanol free 90octane.

Sounds like vaporlock to me. Not sure why it would be a carb if it starts and runs fine cold..

Truely a puzzle


Fuel problems seem unlikely. I always use fresh 91 ethanol free with fuel stabilizer. I've un screwed the cap, and still have problems. I'm thinking perhaps the carb is flooding the engine. After it cools/ rest for a while perhaps the problem lessens?? You can see my op for the list of things I've tried. The local Dolmar/Makita mechanic flat out said "I don't know"
 
Check the valve lash when the engine is hot, there should still be some clearance. If the rocker is touching the valve and you can't get a shim in without resistance then the valves may be tightening up when it gets hot and causing a compression leak. I've seen this on other engines, run great when cold and just [censored] out when they get hot.
 
Originally Posted By: ironman_gq
Check the valve lash when the engine is hot, there should still be some clearance. If the rocker is touching the valve and you can't get a shim in without resistance then the valves may be tightening up when it gets hot and causing a compression leak. I've seen this on other engines, run great when cold and just [censored] out when they get hot.


Ithanks I did already check the valve lash and determined its within specs
 
Originally Posted By: Rab6715
Originally Posted By: Rand
try some fresh ethanol free fuel? Maybe splurge one one of those little cans ethanol free 90octane.

Sounds like vaporlock to me. Not sure why it would be a carb if it starts and runs fine cold..

Truely a puzzle


Fuel problems seem unlikely. I always use fresh 91 ethanol free with fuel stabilizer. I've un screwed the cap, and still have problems. I'm thinking perhaps the carb is flooding the engine. After it cools/ rest for a while perhaps the problem lessens?? You can see my op for the list of things I've tried. The local Dolmar/Makita mechanic flat out said "I don't know"


Well obviously something you have checked doesnt check out or it would be running right? I would still check the gas. super easy to do. Maybe a carb after that or craigslist it and buy something else.
 
Some Husqvarna chainsaws, like the 562XP and 550XP have hot restart problems. The factory fix was some carb. changes and some new air vents in the cover to let hot air out. It was determined the fuel was boiling and causing a vapor lock condition. I have experienced this but only in hot weather above 90 degrees. Every time I refueled(Husqvarna 562XP) it wouldn't start until it cooled off. Even with primer bulbs and pulling fuel through the carb. it still did it. Heat may be your enemy in this case.
 
A friend had a 4 cycle trimmer, possibly a Toro??.... anyways first year it ran great, next year it was extremely hard to start and had trouble idling, even with the choke engaged. Seafoam and other additives made no difference. I tore it down (carb was spotless)and found the way the fuel was metered was the problem. the jet was some sort of nylon or white plastic tube that protruded into the main venture. It had longitudinal slits in it. As the throttle butterfly opened, a small cylindrical metal rod, that was cammed would reveal the longitudinal slits, which effectively was opening up the jet for fuel flow...... If one can even understand my explanation. All this information trapped in words... Anyways I found that the slits were quite narrow and the supply hole at the end of this nylon tube was undersized. Perhaps it collapsed after a season of use? I used a small needle and slightly opened up the supply hole and the slits. Now the girl actually fuels correctly and runs great.
 
Use fresh gas. Most small engine problems are fuel related. You have checked everything else, spend a dollar on some fresh fuel.
 
Skin kit:
Replace all rubber parts every few seasons and they machine will run better.

These diaphragm carbs require some education to work on. First they need flexible skins inside to respond to changes in pressure., if the skins get old and stiff they become unresponsive to changes in engine speed and load. Second is the let off pressure, there are springs on the fulcrum or directly on the fuel inlet needle-seat if the spring is binding or the needle-seat not operating freely then you get fuel supply problems.

An inverted diagram carb, with properly set let off ( pop-off in American ) is incredibly sensitive to the needles and almost fuel injection like in its ability to deliver fuel. But bugger it up and the thing is a dog, today's gas seem to make them into dogs in just a few years.

First place to start is a skin kit and see if that solves the issues.

1611791603393.png
 
Back
Top