Big bore kit on Johnny Red 2065

[njforestfire]

Anyone ever do a big bore kit on a Jonny Red 2065? I have an itch to put one on but am looking for feedback from anyone who has done this conversion. My only concern would be the con rod and crank - if they would hold up with the added torque that it would see. I am the 2nd owner of the saw and it has been babied since. Bought it with only about a dozen tank fulls through it from an old time farmer friend.

 

[Brownpot Deaton]

done one on a husky 365 special....practically brothers...torque increase from bolt on was big....since then modded the muffler, sounds like a stihl now..wired but kool, and widened the exhuast and intake, raised exhuast some and lowered intake some......screamer....still dialing in the carb, being conservative till my tach gets back..... but 28" bar and full chisel square tooth, chews through it like butter... soft woood, buried, it goes through it before i know what happens,...oak...still fast, but can't push on it too much without loosing good speed...


only thing i miss was the lower end torque i had before rasing exhuast, i was thinking about going to a 32" at that point., i could push on it pretty good, but know i have to let it eat through with just some casual manuevarin of the hands...don't get me wrong, i can still push on it, it just cuts much slower....

question i have after doing big bore mod...can a saw still be tuned by ear(four stroking) with a moded muffler, and what size bar should a decent moded muffler mod pull???

is there anything i can do myself to get it to pull and 8 pin at 28"? and can you lighten the 372 big bore pistons??

***if someone has lightened the piston on a 372 big bore, could you please post or pm me with atleast one good picture of what was done, i would greatly appreciate it***

Jordan

 

[Jacob J.]

done one on a husky 365 special....practically brothers...torque increase from bolt on was big....since then modded the muffler, sounds like a stihl now..wired but kool, and widened the exhuast and intake, raised exhuast some and lowered intake some......screamer....still dialing in the carb, being conservative till my tach gets back..... but 28" bar and full chisel square tooth, chews through it like butter... soft woood, buried, it goes through it before i know what happens,...oak...still fast, but can't push on it too much without loosing good speed...


only thing i miss was the lower end torque i had before rasing exhuast, i was thinking about going to a 32" at that point., i could push on it pretty good, but know i have to let it eat through with just some casual manuevarin of the hands...don't get me wrong, i can still push on it, it just cuts much slower....

question i have after doing big bore mod...can a saw still be tuned by ear(four stroking) with a moded muffler, and what size bar should a decent moded muffler mod pull???

is there anything i can do myself to get it to pull and 8 pin at 28"? and can you lighten the 372 big bore pistons??

***if someone has lightened the piston on a 372 big bore, could you please post or pm me with atleast one good picture of what was done, i would greatly appreciate it***

Jordan

I've done a number of these 365/371/372/2171 big bores and the first thing you need to know about them is that the exhaust port is already high from the factory. It's at least .020" higher than stock. When I'm outfitting a pro cutter's saw with one of these I leave the exhaust at the same height and just widen it some.

As far as lightening the piston, it's easy to do and I would recommend at least taking the casting flash on the bottom of the piston off. I'm doing one of these this afternoon and I'll post pics of the piston as it goes.

 

[njforestfire]

I've done a number of these 365/371/372/2171 big bores and the first thing you need to know about them is that the exhaust port is already high from the factory. It's at least .020" higher than stock. When I'm outfitting a pro cutter's saw with one of these I leave the exhaust at the same height and just widen it some.

You 'porting' the opening - smoothing out the flow path on the exhaust?
You also referrence .020 higher - the port in the new jug sits that much higher or is the port that much taller (bigger)? Have you seen, heard or experienced any other problems that come along with going to a BB kit on those saws? i.e. crank, con rod, bearing failures, different carb needed?

 

[Jacob J.]

You 'porting' the opening - smoothing out the flow path on the exhaust?
You also referrence .020 higher - the port in the new jug sits that much higher or is the port that much taller (bigger)? Have you seen, heard or experienced any other problems that come along with going to a BB kit on those saws? i.e. crank, con rod, bearing failures, different carb needed?

The exhaust ports are pretty smooth as is. The widening is to get the additional duration without sacrificing compression. No, the jug doesn't sit higher, it's the port being taller. The BB porting numbers are a bit different than stock and there's also some variation from first generation to second generation (and possibly third generation) kits.

No issues with the con rod, bearings, or carb. The big end rod bearing in the 372 is the same size as some of the older bigger Husky saws- it can take a lot of abuse. I've never heard of a 372 connecting rod breaking other than when a saw was smashed or run over, and I know of 372s that have been run on landings for 6-7 years. The Walbro HD-12A or B is the desirable carb to have if doing this swap, but the Zama works ok too. I didn't care for the HD-6.

 

[Brownpot Deaton]

I've done a number of these 365/371/372/2171 big bores and the first thing you need to know about them is that the exhaust port is already high from the factory. It's at least .020" higher than stock. When I'm outfitting a pro cutter's saw with one of these I leave the exhaust at the same height and just widen it some.

As far as lightening the piston, it's easy to do and I would recommend at least taking the casting flash on the bottom of the piston off. I'm doing one of these this afternoon and I'll post pics of the piston as it goes.

appreciate the info...just for the record, was one of the new nikasil ones..posted some numbers on another website you might be familiar with....
and yes if i had to do it again i would definantly not raise the exhuast....

 

[Crofter]

Out of the box the compression is only 130 psi or so; The exhaust duration is 160 deg or better so if you raise the port any you will lose more on compression. Unless you do a lot of work on the transfers they likely wont run at high enough rpm to take advantage of any longer exhaust duration either. Unless you are prepared to do some machining on the cylinder and piston to get higher compression, I think you are safer to leave them as is. They do run real nice and are not at all peaky.

 

[Brownpot Deaton]

when i degreed mine.after i took the gasket out....the ehuast duration was just under 150....

 

[Crofter]

when i degreed mine.after i took the gasket out....the ehuast duration was just under 150....

I wonder how much consistency there is from one cylinder to the next! One I have here is only 24 mm from top of the exhaust port to the squish band and it needs a bit of clean up that will lose another MM. That would bear watching before you used someone elses dimensions I think.

 

[njforestfire]

Going from the stock 65 cc cylinder to the bigger bore cylinder, can this be compared to using a 371/372 (power and pull) from a stock 2065/365?? I know that there will be a difference but how much? What can it be compared to?

Thanks all for your inputs! I do believe that I will be going this route to make a 'sleeper' J'Red!!)

 

[SawTroll]

I suspect you don't want to do it at one with a Zama carb........

 

[kurtty]

Going from the stock 65 cc cylinder to the bigger bore cylinder, can this be compared to using a 371/372 (power and pull) from a stock 2065/365?? I know that there will be a difference but how much? What can it be compared to?

Thanks all for your inputs! I do believe that I will be going this route to make a 'sleeper' J'Red!!)

i have a 365 special that i put a BB kit on 16 months ago and its stronger than my 372xpw and my 371xp

and sawtroll is correct, the Zama carb wont get enough fuel to the saw. Walbro carb only.

 

[njforestfire]

Good to know about the zama carb - I do believe that is the carb that is in it. I might have a way to increase the jet sizes on that carb.

 

[kurtty]

Good to know about the zama carb - I do believe that is the carb that is in it. I might have a way to increase the jet sizes on that carb.

you might be able to drill it out but i would recomend just buying a walbro carb, they arn't that expensive. and a saw with a new carb and a new top should run like a new saw