Makita 6100 problem

tomalophicon · April 07, 2021, 04:55:15 AM

Hello,
I have a 6100 with an annoying issue.
I bought the saw new around a year ago but have only used around 4 tanks so far. It has done this since the beginning.

The saw starts perfectly, idles perfectly and performs flawlessly when cutting.
However, after it spends time at full throttle and returns to idle it immediately dies. It usually restarts in 2 pulls.
Again i'll rev it up, cut wood and when i release the throttle and it returns to idle the revs drop to where it dies.

I have done my best to tune the carb and iit's got good snappy throttle response and is running slightly rich up top.

Any ideas before I send it back for repair?

Thanks

Tom.

Tacotodd · April 07, 2021, 09:47:20 AM

Did you do a plug check to make sure it's fat, or how do you know? If it's fat, try turning adjustments lean about 3/16 - 1/4 turn lean and see if it still does that. Don't run it so long like this if not. Don't want it to cook itself. Modern saws with readily available mix don't take much turning to do this.

tomalophicon · April 07, 2021, 10:26:25 AM

Hi Tacotodd, thanks for the comment. Are you referring to L or H?
Thanks,
Tom.

Tacotodd · April 07, 2021, 01:17:25 PM

Both, 1st H, checking run; then L, check again.

sawguy21 · April 07, 2021, 03:51:36 PM

You may need to fatten the lo speed slightly when hot. Is the idle speed set just below clutch engagement?

tomalophicon · April 07, 2021, 06:28:54 PM

Thanks both. I'll have another go at adjusting the screws later today.

Spark plug gap was .15mm too narrow (according to NGK specs should be 0.70mm but was 0.55mm). Cleaned and readjusted gap.

DHansen · April 07, 2021, 08:24:20 PM

Instead of just releasing the throttle after the WOT cut, what happens if you release to half throttle for a second then 1/4 throttle then idle? Will it stay idling in that condition. When the throttle snaps shut it will be rich for just a second. Letting it off slowly would eliminate that. If that works, just lean it out slightly, very slightly. Or like the post above mentioned, maybe just set the idle speed up a small amount. It could be set slightly too slow.

tomalophicon · April 08, 2021, 03:19:36 AM

Thanks for all the suggestions.

The plot thickens. Replaced the spark plug with a new item. warmed up the saw and did some cutting. Attempted to tune the L but no affect on RPM until it was fully seated (to the right) and the the revs climbed slightly but the saw didn't die. Then again turned the L screw counter clock wise with no change out to about 4 turns from fully seated. Now I'm more confused than ever.

I did get the high screw to where it was 4 stroking in the cut but it still died.

At that point I put the saw away to do some more research.

Could there be an issue with this carb?

Thanks,

Tom.

Tacotodd · April 08, 2021, 05:49:49 AM

Did you turn the idle speed up yet? That was mentioned in an earlier reply, but you didn't state it.

tomalophicon · April 08, 2021, 06:27:59 AM

Yes, sorry I forgot to mention that. It had little to no effect on idle RPM either.

tomalophicon · April 08, 2021, 06:28:58 AM

Quote from: DHansen on April 07, 2021, 08:24:20 PM
Instead of just releasing the throttle after the WOT cut, what happens if you release to half throttle for a second then 1/4 throttle then idle? Will it stay idling in that condition. When the throttle snaps shut it will be rich for just a second. Letting it off slowly would eliminate that. If that works, just lean it out slightly, very slightly. Or like the post above mentioned, maybe just set the idle speed up a small amount. It could be set slightly too slow.

Yes, if I feather the throttle instead of release it outright I can stop it from stalling.

DHansen · April 08, 2021, 08:44:22 AM

When a throttle closes rapidly, the vacuum on the engine side of the throttle blade will reach it's highest levels. This causing a brief Rich condition. Bump up base idle speed just slightly or lean the idle circuit slightly. What fuel are you using?

tomalophicon · April 08, 2021, 09:13:57 AM

Quote from: DHansen on April 08, 2021, 08:44:22 AM
When a throttle closes rapidly, the vacuum on the engine side of the throttle blade will reach it's highest levels. This causing a brief Rich condition. Bump up base idle speed just slightly or lean the idle circuit slightly. What fuel are you using?

Thanks for the info. I'll try that again tomorrow. The idle speed wasn't changing but I was just checking things over again and the spark plug wasn't tightly seated. Could explain the lack of responsiveness from the adjustment screws?
Fuel is 40:1 with 91 octane. I've just dumped out the tank and will try 50:1 as recommended by the manufacturer. Or any other recommendations?

MakitaDolmar · April 08, 2021, 10:57:52 AM

I'd agree with all in that a minor tweak on the carb screws is probably all that you are off. Of course it would be ideal to adjust with a fixed mixture that you will continue to run. 50:1 is what I believe you'd use along with appropriate or close to appropriate octane. If you tune it on your forever mix you will get a long time out of your adjustments.

DHansen · April 08, 2021, 11:06:33 AM

Start talking oil mix ratios and you'll open a can of worms. I use 40:1, but that is just my preference. Stick with what works best for you. I don't think oil ratio is the issue.

I assume you are using non ethanol fuels? Ethanol blends will cause a leaner air fuel ratio. The more ethanol, the leaner the ratio will be. I'd avoid any ethanol blends.

tomalophicon · April 08, 2021, 04:21:33 PM

Quote from: MakitaDolmar on April 08, 2021, 10:57:52 AM
I'd agree with all in that a minor tweak on the carb screws is probably all that you are off. Of course it would be ideal to adjust with a fixed mixture that you will continue to run. 50:1 is what I believe you'd use along with appropriate or close to appropriate octane. If you tune it on your forever mix you will get a long time out of your adjustments.

Thanks. Fingers crossed the screws respond.
I can use 91, 95 or 98. The manual suggests anything over 88 is sufficient.

tomalophicon · April 08, 2021, 04:25:44 PM

Quote from: DHansen on April 08, 2021, 11:06:33 AM
Start talking oil mix ratios and you'll open a can of worms. I use 40:1, but that is just my preference. Stick with what works best for you. I don't think oil ratio is the issue.

I assume you are using non ethanol fuels? Ethanol blends will cause a leaner air fuel ratio. The more ethanol, the leaner the ratio will be. I'd avoid any ethanol blends.

Thanks. Ill assume ratio is not an issue. The spark screen was clean.
I don't believe there is ethanol. I think by law here it needs to be marked on the pump. The most you can buy is a 10% mix but I avoid it.
Tom.

tomalophicon · April 08, 2021, 11:55:14 PM

Hi guys,

Thank you very much to all on this thread. I rewatched a video on tuning and realised my method for tuning the low made it too lean. Managed to adjust that, adjust the idle screw and readjusted the high. Bucked around 15 metres of hardwood railway sleepers and no stalling at all!

Again, thanks all so much. Was just a tuning issue afterall.

Tom.