14,600 rpm limiter jumping stock Dolmar ps 421

[CoreyB]

Hey guys I have mentioned this in some other threads but actually caught it on camera. Sometimes both my Dolmars (421 & 6100) will jump the rev limiter and just scream. I have seen over 15,000 on the 6100 and over 14,600 on the 421.
I am confused.
Am I tuned to lean?
How can these things spool up that high in stock form and is anyone else noticing it.
I am uploading a video now to my YouTube channel and will post it in the morning I hope. Lol dang slow Internet.

 

[Chainsaw Jim]

What are you tuning them at?

 

[Simondo]

This "over rev" is detected free load I take it and the saws are behaving normal otherwise. Have you retuned both of the saws at some point ? Bringing them way rich first then up to top rpm and into the rev limiter ..then back into rich a tinny bit. As iv said before my 420.. 5105 and 6100 all will pick up rpm a little (regardless of the limiter) as they starve of fuel if the tank is run to empty. I make this point around what shows at a "fuel flow change " not saying that this "Is" the issue. Are the coils tight ? not moved...Worth checking the coil gap as it needs to be right - .25 .30 mm ..10-12 thou from 6100 manual ..420(421) likely the same . Of corse the coils could be failing but "both saws " doing the same thing !! not so sure on that one .

 

[bikemike]

This "over rev" is detected free load I take it and the saws are behaving normal otherwise. Have you retuned both of the saws at some point ? Bringing them way rich first then up to top rpm and into the rev limiter ..then back into rich a tinny bit. As iv said before my 420.. 5105 and 6100 all will pick up rpm a little (regardless of the limiter) as they starve of fuel if the tank is run to empty. I make this point around what shows at a "fuel flow change " not saying that this "Is" the issue. Are the coils tight ? not moved...Worth checking the coil gap as it needs to be right - .25 .30 mm ..10-12 thou from 6100 manual ..420(421) likely the same . Of corse the coils could be failing but "both saws " doing the same thing !! not so sure on that one .

Could be fuel and exhaust temps, or a ember of carbon but if it's tuned rite and it's your ignition that is not cutting out then don't replace the coils. if both saws are doing it then I think it's a tuning issue and diesel effects are happening

 

[Simondo]

Could be fuel and exhaust temps, or a ember of carbon but if it's tuned rite and it's your ignition that is not cutting out then don't replace the coils. if both saws are doing it then I think it's a tuning issue and diesel effects are happening

Assume your post was meant to be tagged onto Cory's post. Not having issue with my saws Mike...just commenting that i have had a RMP lift on 3 "new " saws with the fuel running out. Other than that mine are not giving agro.

 

[bikemike]

Sorry I just hit reply to this I've seen it happen on a few saws myself too and it was a fuel lean out issue.

 

[CoreyB]

Ok guys here is the Video. A little long but I didn't want to edit it down.
This is not happening because of low fuel.
@Red97 @Miller Mod Saws
Would you mind watching and sharing any input.

 

[CoreyB]

What are you tuning them at?

The 421 has been turned right at 13,320 - 13,500
The 6100 13,500- 13,620

 

[bikemike]

How long have you had your saws, and what fuel do you run

 

[CoreyB]

How long have you had your saws, and what fuel do you run

The 6100 for a bit over a year and the 421 for 3 months. I use a local 91 octane e-free with either red armor or Dolmar synthetic. I have also used vp 40:1 and a little true fuel 40:1

 

[bikemike]

Good chance that rules out cracked fuel lines. the few dolams that been run a mn gtg were screamers even in the cut.

 

[Miller Mod Saws]

Ok guys here is the Video. A little long but I didn't want to edit it down.
This is not happening because of low fuel.
@Red97 @Miller Mod Saws
Would you mind watching and sharing any input.

I'll watch the vid this evening when I can hear what's going on. I don't see any issue though as long as your saw is tuned right.

 

[Simondo]

Ok guys here is the Video. A little long but I didn't want to edit it down.
This is not happening because of low fuel.
@Red97 @Miller Mod Saws
Would you mind watching and sharing any input.

Cory ..Im not suggesting that you are getting the fuel run out that i talk about...i use it as a example of when the fuel supply is compromised and then the RPM increases..."Regardless of the limiter".. You "may" be getting a fuel starvation or a leaning down situation .
PS: Watched vid and to be honest it sounds good , yea ok the peak is over the theoretical limit but its the sustained rpm that counts. Give it some more on the H to bring it in at 13000-13200 then really get it hot and see where you are.

 

[Adirondackstihl]

@166
@cuttinscott

 

[Simondo]

Ok guys here is the Video. A little long but I didn't want to edit it down.
This is not happening because of low fuel.
@Red97 @Miller Mod Saws
Would you mind watching and sharing any input.

As a add on.....That is one pretty place you have there

 

[166]

Set the 421 at 13,000 and try it again. Every 420/421/4300 we've sold is happy at 13,000 RPM. Maybe 13,200 tops if the saw has some hours on it.

Same thing with the 6100. Set it at 13,500 max and both saws should act better.

Most tachometers will not give a true reading on the newer generation saws. The rev limiter gives the tach a false reading.

 

[5000+]

Set the 421 at 13,000 and try it again. Every 420/421/4300 we've sold is happy at 13,000 RPM. Maybe 13,200 tops if the saw has some hours on it.

Same thing with the 6100. Set it at 13,500 max and both saws should act better.

Most tachometers will not give a true reading on the newer generation saws. The rev limiter gives the tach a false reading.

But why does the rpm flair up past the limiter sometimes? I think You can hear it on the limiter most times. I know the tach will not read correctly near or on the limiter, but you can clearly hear it scream like the limiter is not working.

 

[CR888]

This is perfectly normal for the 6100 & 421. As they break in their awesomeness increases and they break through the limiter, no ignition module can hold them back! The awesome factor increases with the use of Red Armor.....a dangerous combination for sure. If they continue to 'break the rules' sit them on the ground and pour beer on them to cool them off.

 

[CoreyB]

Set the 421 at 13,000 and try it again. Every 420/421/4300 we've sold is happy at 13,000 RPM. Maybe 13,200 tops if the saw has some hours on it.

Same thing with the 6100. Set it at 13,500 max and both saws should act better.

Most tachometers will not give a true reading on the newer generation saws. The rev limiter gives the tach a false reading.

I will set them fat and creep up to those rpm. In reality it happens so rarely that I doubt I will see it again for awhile. I was just "lucky" to catch it on camera twice.
I was wondering if it would be possible for a builder to manipulate to their advantage while searching for an unlimited coil.

 

[166]

If these saws are still on the original fuel filter swap them out. I recommend the Husqvarna style fuel filter.

The saws are set to lean. Swap the fuel filters and retune.

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