My dad was a firm believer in "don't ever throw anything away" & that's been passed on to me.Sometimes it comes in handy if I can remember where I put it.My neighbor says "do you know how long it's gonna take me & your son to sell all the saws you have"?I told him "if you have as much fun selling them as I did collecting & fixing them,then God bless ya".
McCulloch Chain Saws
- Thread starter Bruce Hopf
- Start date
Help Support Arborist Forum:
matt_lamb_160
ArboristSite Operative
McCulloch Ports 450 vs Super 250
I am looking to build a saw inspired by the Mc49 kart engine. I have access to a 250 Super and a 450. Which has the better porting standard and what makes it better? I am also keen to know how they compare to the older 1-51 blocks? I can get any number of 250 engines, but I am not aware of any advantage over a Super 250. I have been looking at this particular topic and it isn't clear to me which is the best.
Sorry if I have butted into the middle of a conversation!
I am looking to build a saw inspired by the Mc49 kart engine. I have access to a 250 Super and a 450. Which has the better porting standard and what makes it better? I am also keen to know how they compare to the older 1-51 blocks? I can get any number of 250 engines, but I am not aware of any advantage over a Super 250. I have been looking at this particular topic and it isn't clear to me which is the best.
Sorry if I have butted into the middle of a conversation!
- Joined
- Jan 11, 2014
- Messages
- 3,379
- Reaction score
- 3,997
The super 250 is going to have the best porting of all the 87cc saws by far. I've had a few of them and a 550 regular and a 550 super. Those bigger saws had more torque but way less rpm once the reeds on the super 250 opened up. Those reeds almost seem like the saw gains a higher gear or has nitrous oxide when under a hard load. I dunno on the 450, but it doesn't have near the reputation that the super 250 has earned.
Did anyone ever find an alternate to the 67906 FW side seal?
I can't seem to find it in any seal co. catalog.
I believe it's 0.562" X 1.5" X 0.25" but I'm not sure about the shaft size or housing bore. As far as I know I don't have any saws using that seal.
I can't seem to find it in any seal co. catalog.
I believe it's 0.562" X 1.5" X 0.25" but I'm not sure about the shaft size or housing bore. As far as I know I don't have any saws using that seal.
Do you mean 1.379" OD? I just installed Timken 471551 on my sp81.
https://www.motionindustries.com/productDetail.jsp?sku=01316254
Just curious..., have you done a vacuum/pressure test on the shortblock?
Nope not yet.
You may want to consider it before too much more re-assembly to ensure the case and seals are tight..., just for the peace of mind. Standard practice for me these days. Better to find a leak now than after the saw is back together and not running right because of one.
National 471551 is used to replace MAC PN's 65746 and 61618. A different seal was used on some of the 10 series on the FW side, 67906
Thanks for the reply though.
Gotcha fossil. Do you know what 10 series saws use the 67906?
10-10S,
10-10 600001, 600002,
Pro 10-10A 600013,
Super 10-10A 600007,
10-10A IPL 68719 (1968),
PM55.
Those are a few that I checked on IPL's that use 67906
I wouldn't be surprised if there were more. Mark said he was able to find a replacement for 67906 but I'll be darned if I can find it. Maybe I have the OD wrong.
The PM60 and larger 10 series seem to use 65746 and 61618 which are the same seal.
Gotcha, good to know, I was under the impression the majority of 10 series saws used the seal I mentioned. After I finish up this 81 I'm gonna try building a 10-10s with lighter weight tins, so I'll be finding out what seals I need.
Just an observation....I just cleaned up my fixed jet carb for the 81. It has a #31 hi speed jet and my ipl says it should have a #29. It also states #26 and #28 are going used for high elevation. I'm guessing the bigger the number the bigger the jet size. Am I gonna run too rich with a 31 in there?
Yes that number corresponds to the opening or hole size in the jet. Its a measurement of thousandths according to bob johnson. He explained it to me that way last year.
As far as too rich? A test would be required. If you fire it up and it runs great and cuts good then leave it be. If not and youd like to change it then by all means. Ive got a sp81 with the fixed jet and it runs great. I put a sdc 37 on another one and it performs well also. Little snappier maybe too. My favorite mac i use often as i can. I just drilled a small hole in the air box for a screwdriver and used a plug for the hole. Works fine
As far as too rich? A test would be required. If you fire it up and it runs great and cuts good then leave it be. If not and youd like to change it then by all means. Ive got a sp81 with the fixed jet and it runs great. I put a sdc 37 on another one and it performs well also. Little snappier maybe too. My favorite mac i use often as i can. I just drilled a small hole in the air box for a screwdriver and used a plug for the hole. Works fine
Well, testing done. She rips. 4 strokes nicely unloaded and hunkers right down nicely when loaded up. Just need to find myself a bucking spike and this one's ready for regular service.
Here are a couple templates if you have access to a plasma cutter. I have the larger one on my SP81. It's a modified Stihl spike from one of their older large saws. I like it.
Thanks Pogo!
Your 81 looks nice.
Thank you. Turned out ok even with a quick rattle can paint job. Hasn't seen much use since I rebuilt it. Had a chip ignition and a broken crank when I got it. Converted back to points when I rebuilt and I wasn't as careful with them as I should have been when cleaning and gapping..., which led to a less than anticipated runner and enough resulting frustration to put it on the shelf for another day. Just got back around to it this spring and it's running much better after spending more time and attention to detail with the points. Has yet to be put through its paces, but the chain is sharp and it's ready to go when the time comes.
matt_lamb_160
ArboristSite Operative
Thanks for the reply. I have heard that about the 550 saws before and put it down to the longer stroke. The 450 having the same stroke and a slightly larger bore than the Super 250 I thought may be different. I wonder what the difference in the porting is?
Similar threads
Want to Buy
McCulloch Super 250
