Makita 7900 seems hot

[Greenerpastures]

Hi everyone

I have a Makita 7900, the one with the cat.
I only used it an hour to test it out when I got it, and it sounded and ran fine.
I took it out today for an hour, and was only cutting light bushes and limbs.

I put my had on the fins and they are quite hot, I took out the plug and it was almost too
hot to hold.
The plug was a little oily, which is fine for the amount of oil I have in the mix.
She is not running lean either.

Should I be worried, as you can tell, this saw is new and am doing some work with it
before the warranty is up, and have a stack of logs to cut, not heavy work at all.

Never having a Makita before or working with one I am not sure if the saw is running hot
and this is a sign of something not quite right. It sounds fine, and fourstrokes well, and according
the the condition of the plug all seems good, except for the quite hot fins and the nut around the plug being almost too
hot to hold.
Saw also started to run faster at idle, so adjusted this down.

Thanks, john

 

[tpence2177]

Sounds like the fins are doing what they are supposed to do which is dissipate heat. Plug always gets to hot to hold after just a few minutes of running.


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[blsnelling]

It's an engine...they get hot

 

[Greenerpastures]

Thanks to all, I know they get hot, have nothing to compare it with only my Shindaiwa 490,
which runs a lot cooler doing the same work this morning.
So had me thinking.
Am off now to look at the Echo CS-501, see what one looks like in the real world.

 

[Greenerpastures]

Well, I got the Echo CS-501, and in the meantime will be cutting back the
mixture on the Makita, it is putting a little out the exhaust, and combined
with the obstructions in the muffler would make things hotter than need be.

The Shindaiwa 490 even though not hot, is also putting some fuel out the muffler,
so am thinking it could be this particular mix am using, either way the Makita puts
out more and is well and truly fourstroking, so will cut back a little, and test again,
This particual mix is 37:1, where my usual is 40:1, would seem these saws with epa rubbish
are more sensitive to the mix.

Looked in the CS-501 booklet and they recommend 50:1 mix, the guy in the shop
insisted not to go 40:1, I asked him what would happen if someone went 40:1,
he said it would come out the exhaust, so am thinking now that my hot Makita
may be suffering a little of both, too rich, and too much oil in the mix, oil am told
has more omph than the petrol when burning, but am I burning it and causing extra heat
or am I dumping it out the exhaust and slowing down the evacuation processes and this
is what is causing my hottish Makita. Either way, easy enough to sort.

 

[tpence2177]

Sounds like you need to just open up the mufflers on them and run 40:1. I’ve seen people on this forum that have no carbon buildup or any issues running 36:1 or lower it just has to deal with having the right tune. That being said I’ve never been a huge fan of 50:1 myself though so take that for what you will.


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[Greenerpastures]

Sounds like you need to just open up the mufflers on them and run 40:1. I’ve seen people on this forum that have no carbon buildup or any issues running 36:1 or lower it just has to deal with having the right tune. That being said I’ve never been a huge fan of 50:1 myself though so take that for what you will.


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Hi tpence2177
I won't be sticking to 50:1 for long on the CS-501, will get it broke in a bit, then gradually change the mix
and see what heppens.
Am going to set the other two up with 40:1, run them an hour or so, to see how they proform, then remove
the spark arrestors from both for cleaning, and leave them off, until I get time to sort the muffleer mods.
I want to go to the saw shops to try and find scrapped ones that I can get mufflers off, that way I won't need
to hack up my own.

 

[166]

Hi everyone

I have a Makita 7900, the one with the cat.
I only used it an hour to test it out when I got it, and it sounded and ran fine.
I took it out today for an hour, and was only cutting light bushes and limbs.

I put my had on the fins and they are quite hot, I took out the plug and it was almost too
hot to hold.
The plug was a little oily, which is fine for the amount of oil I have in the mix.
She is not running lean either.

Should I be worried, as you can tell, this saw is new and am doing some work with it
before the warranty is up, and have a stack of logs to cut, not heavy work at all.

Never having a Makita before or working with one I am not sure if the saw is running hot
and this is a sign of something not quite right. It sounds fine, and fourstrokes well, and according
the the condition of the plug all seems good, except for the quite hot fins and the nut around the plug being almost too
hot to hold.
Saw also started to run faster at idle, so adjusted this down.

Thanks, john

You're 7900 does not have a catalytic converter.

 

[KiwiBro]

It's not hot until you can hear the fuel boiling in the tank.

 

[Greenerpastures]

‎Hi, I am not sure about this, as my saw is a EA7900P45E, bought in the UK.
And the video I have seen all show what looks like a circle crammed with
honeycomb inside the muffler, that people are removing to help the saw to bereath.

I am not sure now what to do regarding modding the muffler as if there is no cat in
there then I would be wasitng money and time replacing this muffler with what I understand
to be a non cat one.

Thanks for pointing this out to me.

 

[Greenerpastures]

It's not hot until you can hear the fuel boiling in the tank.

Hi, KiwiBro, I have not ever heard this happen, in any saw, this country is cold, so ambient temperature is not adding to what
I think is a hottish running saw, today I will get a chance to try a 40:1 mix, and see if there is any difference from the 37:1
that it is currently running, though my Shindaiwa runs the same and runs cooler.
Do you run one of the Makits

Thanks for commenting

 

[KiwiBro]

Yes, but the Dolmar flavour.

 

[Greenerpastures]

Yes, but the Dolmar flavour.

View attachment 603219

Nice piece of wood there, what oil mix are you running, have you done any modifications, even just removed the spark arrestor.

 

[KiwiBro]

40:1.
No modifications.
Just swapped the standard filter for their heavy duty filter option.

 

[Greenerpastures]

Ok, do you know if there is a cat in the muffler of your saw, someone has now told me
there is no cat in mine, but most others talk of modding this muffler and cutting the insides
out, so am at a stand still now regarding buying an aftermarket non cat muffler.

Your filter upgrade is a good choice, dust is a killer in any engine.

 

[KiwiBro]

I don't think it does but to be honest I've not really looked because it breaths fine as is for cross cutting duties. If milling, I'd pay more attention with a view to removing restrictions because on the few occasions I have ripped a log with the 7900 to break it down so my winch could drag it, I did have a gut feeling it was getting too hot for comfort. But that was also using the stock oiler which on 32" bars and in the sort of timber I was ripping, was definitely asking too much of it.

 

[Greenerpastures]

I don't think it does but to be honest I've not really looked because it breaths fine as is for cross cutting duties. If milling, I'd pay more attention with a view to removing restrictions because on the few occasions I have ripped a log with the 7900 to break it down so my winch could drag it, I did have a gut feeling it was getting too hot for comfort. But that was also using the stock oiler which on 32" bars and in the sort of timber I was ripping, was definitely asking too much of it.

Hi KiwiBro
Thanks for explaining.
I have never heard of anyone changing the stock oiler, lots of mods but not heard about an upgrade for the oiler.
In any event, my saw has only a few hours on it, so today I took off the muffler, and all is good inside the saw,
I am glad I did take the muffler off as when I was inspecting it to put it back on, I found the edges on the piece that
goes into the cylinder to be sharp, I filed the two sharp edges off, as I think through time they would deteriate and
fall off, even more alarming was there was a small shaving of steel between the gasket and the muffler, there is a
recess there where the piece that protrudes into the saw comes through the muffler housing, took it out too, so
now am happy there is nothing in that area that could be problematic in the future.

I also removed the spark arrester for a look, that is a small hole for exhaust gasses to escape through, and the spark
arrester compounds it more, so its not going on again, not much danger of fire here, and if there is it is now secured
inside the cover that houses the carb area, so I can pop it in.

Seeing what I had, I now understand the mixture and carb settings on this saw need to be spot on, else heat.
Next up is to re introduce my 40:1 mix, heat up and tune up.

 

[KiwiBro]

Onya.
There's a modification to the stock oiler to increase output. Not sure if there is a different oiler option or after market options.
Good luck with the tuning and creeping up on the limiter.
The stock standard air filter works but clogged too quickly and I found it a PITA to keep unclogging so often. I am not sure if anyone else has found this to be the case but I also find the saw has a pretty narrow range where it stays in tune, and the clogging standard filter was really throwing it out. Actually, I had a really humid day amongst intermittent clouds and even that was messing with the tune. Haven't had it at much elevation but would be keen to learn if others find they are retuning their 7900/7901/7910 more than other saws.

 

[Greenerpastures]

KiwiBro, I think you are going to need to gut that muffler to keep your saw cool in varying conditions, people say it gains power from this, more than your filter change will give it, but you definitely need that filter change for dusty conditions and more time between cleans, maybe a semi skip chain would ease the pressure in big wood. I have rarely much big wood, so stock saw is ok, though muffler l know is restrictive part of these saws.
Regards, john

 

[KiwiBro]

It doesn't suffer from a lack of power and if in bigger wood or needing to rip, I've now got my 395. So, I'll leave it stock. Might be selling it soon anyway. But thanks for the suggestions.