61 to 272-clearance questions

[spike60]

@svk and I have exchanged some PM's on this project and here's some pics to share with everyone. Gonna be a lot of pics here. Mostly want to look at the top cover and muffler fit up when putting a 272 kit on one of the early twin coil saws. This one I did on an older gray top 61. First pic shows the cylinder on the saw. The 272 is a little bit taller than the 61 or 266 jugs, but the fins also create some interference. Thing to look at is the top fin extends as far as the rest of them. The second pic is a 61 cylinder; notice the top fin is rebated a bit. The top fin of the 272 cylinder will touch the top cover a little bit which may be seen in the 3rd pic. Really not a big deal.

 

[spike60]

There are essentially two molds that were used on these covers. The early ones are the whit top 61's and the orange 162SE covers. Then there were the gray 61/66 cover and the orange 266XP cover. The early ones are lower and need to be cut to fit on the 272 jug. The later ones should fit with no problem. In my case the cover is in contact with the spark plug boot but it fits OK; no forcing it to get it on. This is an OEM jug. Steve has a problem with the spark plug on his project, but is using an AM cylinder. My guess is that the plug angle could be a little different there than OEM. Mufflers up next..............

 

[spike60]

New taller muffler on the left, and an early lower profile muffler on the right. New muffs probably flow a little better, but they will be in contact with the top cover as seen in the second pic. I'm not worried about the deal with the top fin, but the muffler will definitely melt the top cover. None of these covers are available, and I don't want to wreck the cover, so I went with the original muffler.

 

[spike60]

Most of the early mufflers are baffled, but I had one that was open inside, so that's what I went with. The studs that were used on the early mufflers fit right into the 272 jug. Folded the opening back but stuck with the twin outlets to keep it stock looking. Figure at some point @weimedog might be wondering why this old 61 runs so good. Does have a decent bark to it this way.

 

[spike60]

The finished project. @weimedog might recognize this wrap handle that he traded me a couple years ago. Bent the metal brake handle so it would work with the wrap, which comes back a little farther. Note: When ever using one of these old side covers with the metal brake, you have to use a plug instead of a deco as it will not clear the older handle. Gotta get a decal for that starter don't I.

 

[svk]

Looking good Bob!

I will figure out which AM top end I have and post up so others can avoid that brand and not have to deal with the clearance problems I encountered. As everything in this project came to me secondhand it has been a learning experience. We have a little bit of a custom top cover coming and I will share those photos as well once it is done.

The good thing is I now also have a complete top end and intake system for a 61 as well as a running 272.

 

[weimedog]

Cool project....there is some maple out there that needs that saws undivided attention! Need to fill another cart..

 

[svk]

Edit: My cylinder copies a 272 plug angle. Which doesn't work with a 266 top cover. Should have the cover issue solved by early next week.

It's too bad the newer 272 cover has a different bolt pattern.

 

[Cantdog]

Yep... plug angle is the biggest problem when converting these old saws....I was going to build a "sleeper" 630 with a 268XP P&C.....but no matter what I did the air filter cover would not go on due to spark plug interference......even using the tiniest spark plug I could find and the thinnest boot....everything fit fine under a Husky gray top.....but gray is not black so ended up using a 670 cyl......same difference performance wise and it will fit fine under the Jonsered cover...but of course it not a 272 either.....but ported it comes damn close...

 

[Cantdog]

Here is a pic showing some differences between cyls and various plug angles. The cyl on the left is a 272XP cyl......the one in the middle is a 630 cyl and the one on the right is a 268XP cyl.......note the 272 and 268 plug angles are the same but the Jonsered cyl has a much lower plug angle....the 670 cyl has the same plug angle as the 630...sorry...no pic of that......but trust me ....LOL!!

 

[svk]

Is there a plug smaller/shorter than the standard chainsaw plug? Every one I have here across three brands are exactly the same size.

 

[svk]

Looks pretty close to the OE 272...

 

[Cantdog]

Is there a plug smaller/shorter than the standard chainsaw plug? Every one I have here across three brands are exactly the same size.

Yes but I can't tell you what brand.....would have to be at the shop. LOL......one of the by-products of acquiring old beat/broken saws is that when a saw is found not to start....what is the first thing most folks do?....put in a brand new plug ...right?? If the saw is all done a new plug won't be the cure. So I have a LARGE box full of brand new plugs of various makes and heat ranges.....I will truly never have to EVAH buy another spark plug for one of my chainsaws..!! LOL!!!

 

[Cantdog]

View attachment 529902

Looks pretty close to the OE 272...

Yes it does.....probably is exactly the same angle...I don't really know whether a high angle or low angle makes any difference at all performance wise......logic would say the steeper angle would be more efficient.......but logic is not always meaningful in these 2 stroke motors....

 

[svk]

Well at least it makes sense for my cylinder that they copied an OE cylinder and didn't just put it some random angle.

 

[burnses]

I tried my white top on a 61 with a 272 cylinder but not even close but if I can get a gray top cover prob get back to it got a nice top end and carb...

 

[spike60]

Yep... plug angle is the biggest problem when converting these old saws....I was going to build a "sleeper" 630 with a 268XP P&C.....but no matter what I did the air filter cover would not go on due to spark plug interference......even using the tiniest spark plug I could find and the thinnest boot....everything fit fine under a Husky gray top.....but gray is not black so ended up using a 670 cyl......same difference performance wise and it will fit fine under the Jonsered cover...but of course it not a 272 either.....but ported it comes damn close...

Ya know Robin, you could always paint that Husky top.................black not silver. Sorry, it was just there and I had to say it.

But the 670 cylinder is right there performance wise and is more "proper" to the family. I have a 625 with a 670 top end. Ratty, ugly saw but it runs great. Next project is to put a 272 top end on one. Jonsered never got the 52mm upgrade like Husky did, and I think its time we corrected that slight to the Red side of the family. So, I'm going to make myself a "672 Super". I expect that the taller top cover from the later single coil saws should fit OK. (Guessing your project was a twin coil saw?)

 

[Cantdog]

Yes it was a twin coil model and I believe you are correct that the later single coil top covers will work with a 52 mm cyl. I have one in the "project" section that is slated to be a "672"...I did consider painting the top...but it would only fool folks that didn't know better....and Silver....well.....LOL!! Plus I prefer simply removing the Jonsered air box cover as opposed to the Husky system where the entire top must be removed to clean the filter.
So I went in the other direction on that saw.....I had a velocity stack from a 670 West Coast and a gray 61 top cover that was cracked in exactly the right place!! LOL!!

 

[spike60]

That looks good Robin. Got rid of the incorrect decal in the process.

I'll get some pics of both Jonsered tops sitting on a 272 cylinder. Both early and late Jonsered tops are NLA of course. At least with Husky, you can still get the tops for the single coil saws.

 

[spike60]

Here is a pic showing some differences between cyls and various plug angles. The cyl on the left is a 272XP cyl......the one in the middle is a 630 cyl and the one on the right is a 268XP cyl.......note the 272 and 268 plug angles are the same but the Jonsered cyl has a much lower plug angle....the 670 cyl has the same plug angle as the 630...sorry...no pic of that......but trust me ....LOL!!

I certainly trust you buddy, but we have a puzzler to solve here. I have some 670's that share the 272 plug angle. They are single coil saws from 92 and 97. I have an additional cylinder that I installed on a 1987 625. It also has the taller plug. As does a 1992 625II. My guess as to what's going on here: There are early and late 625 and 670 cylinders. (630 remained the same throughout it's run). What I remember is that they went to a longer "neck" on the intake port when they switched from the wire boot clamp to the band style clamp. (And the intake boots were also changed). Could they have changed the plug angle at the same time? I really don't know and I don't have any of the early wire clamp cylinders to look at. So, you're going to have to clear this up my friend.

On to the top covers themselves, The cylinder cover really doesn't matter here. The later air filter covers all have a bigger spark plug hood, including the 630 even though it's plug angle never changed. The new filter cover will fit the early cylinder cover. Of course none of them are available so we have to make do with what we have. My 625/70 has the old filter cover and while there is that unsightly 1/4" gap because of the poor fit, it more or less works. The advantage with the 2 piece Jonsered set up is that the cylinder cover can still be secured properly.

Still the most fun chassis project wise for me. Another home grown model I built is a "636 Super". Used a 50mm 266XP cylinder on a 1985 630. 266 has the same plug angle as the 630, and requires zero changes to the intake. Same intake block, gaskets. Gonna run that one tomorrow.