254/262 carb - difference between them

[Tor R]

Hi,

I am into carbs nowadays

I have a collection HDA 35A, HDA 35B for the 254's.
A collection HDA 120, HDA 87 for the 262's.
I know the HDA 87 is the one to have for the 262, so all off those get a full carb cleaning and rebuild.

What is the different between the HDA 35, 120 and 144?

On all off them, the little fuel niddle inside have a plastic/rubber tip while a brand new ones have metal also on the tip.
Why? (Was the old niddle type a lousy one)

Anything else I should be aware off?
Thanks for any help and input.

Regards
Tor

 

[M&Rtree]

Venturi sizes are different between them all. 35 being smallest, 87 largest.

 

[Tor R]

But what about 120 vs 144?

 

[M&Rtree]

Those two are very similar in size and performance I believe. Never had a 120 though.

 

[Tor R]

Thanks alot for your reply.
Do you know why they changed the fuel niddle from plastic tip to metal tip?

 

[decableguy2000]

The one differences I noticed is the 144 has limit caps and the 120 doesn't. Maybe a different jet but I don't know for sure.

Jeremy

 

[rattler362]

This might help
http://www.walbro.com/parts-service.aspx

 

[Tor R]

After studying gasket sets I have concluded that they are identical from 35B, 120 and 87, I thought actually that they were different since there are different order numbers in the IPL for the 262.
Gasket Sets 503 54 76 01, gaskets and fuel - metering diaphragm.
Gasket Sets 501 66 84 01 is complete, includes fuel innlet screen, fulcrum pin, plug, innlet niddle and lever. There is also another little plug where I haven't figure out where it should be placed.

Will see if I can take one picture of old - new Innlet niddle and post it, pictures say more then words

Since the venturi is bigger on HDA-120, and that HDA-144 is quite similar, I'm going to use them on the 254's I will build.

 

[SawTroll]

....

Since the venturi is bigger on HDA-120, and that HDA-144 is quite similar, I'm going to use them on the 254's I will build.

Should be better than the HDA-35, but still not larger than the 346xp etc carbs. HDA-87 could be worth trying even on the 254 I guess.....?

 

[Tor R]

Should be better than the HDA-35, but still not larger than the 346xp etc carbs. HDA-87 could be worth trying even on the 254 I guess.....?

I do not know if it is normal, would almost believe that a 254's should be modified thoroughly before hda-87 will make a difference. I read a place here that hda-144 resulted in a noticeable increase in performance on 254.
I must study the intake of 254 to see if there is enough room for the increase. The idea is very tempting, I have one pair extra 87 to spare.

 

[Tor R]

Here is a picture of the innlet niddle, old plastic style to the left, the new style looks to be pure metal.

 

[M&Rtree]

I gained torque going from the 35 to a 144 on my 254. You can feel a difference in a large log.

 

[Tor R]

I gained torque going from the 35 to a 144 on my 254. You can feel a difference in a large log.

Thanks, I knew it was either you or rattler who had mention it before, I consider both the two of you to be very talented, when you get something to work well, it is worth doing it myself also.
I sure starts to get a plan for my rebuilds of the 254's and 262's now

 

[BigDee]

I replaced a 35 carb on a good running 254 with a 120 and it made an easily noticeable improvement in rev up speed and power. Don

 

[Tor R]

I replaced a 35 carb on a good running 254 with a 120 and it made an easily noticeable improvement in rev up speed and power. Don

Thank you. It looks the gain is there using either 120 or 144, and that is what my 254's will run with when they get a full overhaul, there is no reason for me to spend time on any of those 35.
I will also try out the suggestion from sawtroll with using a 87 carb, if the inntake is big enough though.

 

[BigDee]

Before making the switch, I drilled out the intake, removed the base gasket and opened the exhaust. I thought the saw ran well before I changed the carb. But the 120 made a noticeable improvement.

Many thanks to all the Arboristsite members who helped me get this far.

 

[Tor R]

Before making the switch, I drilled out the intake, removed the base gasket and opened the exhaust. I thought the saw ran well before I changed the carb. But the 120 made a noticeable improvement.

Many thanks to all the Arboristsite members who helped me get this far.

Thank you for the advise, I will work a bit with the intake, a thinner base gasket and mm.
I have 3 different type cylinder to the 254, I am excited to try out the model 87 cylinder I have.

Oh yes, people on AS are awesome!

 

[BigDee]

The 87 will bolt up but I could not tell the difference. But I have not touched the cylinders on mine except to barely touch the exhaust.

I have had a 266se since 1985, untouched, and I think the adjusted 254s are almost its equal except in full bar cuts.

 

[super3]

Filter elbow and especially filter inlet are a bottle neck on the 254 also. Open them both up as much as you can.
Close to the same gains as the carb swap.

 

[BigDee]

I know you meant carbs, (be careful to watch your carbs if you have a weight prob) but there are at least 3 kinds of 254 cylinders, Mahle, Kolbenschmitt, and Mahle's with decomp holes. And I think some of the 154s are even a bit smaller in the combustion area. Some do not have enough squish to omit the gasket.