MS361 Big Bore Kit Review

[blsnelling]

Yes, you read that right. I have setting on my desk here a brand new prototype MS361 BB kit. Bore size is 49mm resulting in a displacement of 64.1cc, up from 59.0 stock. So far I've visually inspected, measured specs, and taken pictures. I've not yet put the parts on my saw. That will come soon enough. The P&C look very good. I intend for this is to be a fair honest report. Please keep this thread clean and on topic as I would like for it to be something of a product review than can be useful to others.

Here's some of the specs.

1. Piston Weight = 2.4 oz
2. Wrist Pin Weight = 0.4 oz
3. Cylinder Weight = 16.4 oz
4. Crown thickness above top ring groove = 0.135". Plenty of room for a popup.
5. Ring thickness = 0.047" = 1.2mm
6. Ring thickness = 0.009" and 0.011"
7. Piston to cylinder clearance = 0.0015".

Here are some notes I've made so far.

1. If the piston is twisted perhaps 45* in the bore, it gets a little snug. The corners of the tails of the cylinder that fit into the case are 0.001" tighter than in the middle. It's a non issue when lined up as it would be when assembled. These never contact the piston during operation.
2. There is one small pourous cavity in combustion chamber, a non-issue.
3. Stihl style circlips are now used and the piston is relieve likewise for removal. A nice improvement the customers have called for.
4. The ports are very nicely beveled.
5. The NiSi coating and honing looks nice.
6. Lots of extra skirt width and meat in the ports for porting.
7. The piston skirt does not even come close to freeporting the exhaust port at TDC.

 

[blsnelling]

 

[blsnelling]

Lots of rooom for widening the intake port.

Lots of room on the exhaust too.

 

[Cheese]

So can we ask you about this?

Seems like a BB 361 with port work like you have done, would be a fun, light work saw. I am still having mixed emotions about how the 361 feels in my hands compared to the bigger pro saws.

Looking forward to more pictures, video and your usual attention to detail.

 

[GASoline71]

Why on earth would you want a BB on a 59cc saw?

However... I think the big bore kits are a waste of money... but that's just me.

Gary

 

[Lakeside53]

What about the port timing? Did they just copy a stock cylinder and then bore it out (like the earleir 066BB kits...), or are they adjusted?

Your comment about the piston being tight when rotated... lolol.. Hope they are aren't like that with a 1.5 thou clearance.... have you ever seen an OEM piston/cylinder like that? I'd send it back and ask for another.

I see it has the same old crappy non-tapered (lightened) pins..

So Brad - how about testing it as-is before porting it...??

 

[blsnelling]

I don't think Baileys claims for these to be of the same standards as OEM Mahle P&C kits. However, they serve as a valuable option for the saw owner that either doesn't want to spend as much, or one that wants more CCs. I think it's great. The more options the merrier.

I have not assembled it yet to measure port timing.

 

[GASoline71]

Toss those crappy wrist pin clips too...

Gary

 

[blsnelling]

Toss those crappy wrist pin clips too...

Gary

They look just like Stihls now. Did you see the pic? Might be cheaper metal, but at least they gave us the style we've been asking for.

 

[Lakeside53]

They look just like Stihls now. Did you see the pic? Might be cheaper metal, but at least they gave us the style we've been asking for.

Unless then are a DIN standard clip, throw them. The CHICOM junk TS400 piston sets have has "stihl looking" clips for years. Still junk.

But, it probably won't matter with a binding piston anyhow

 

[stihl only]

Could you include the weights of the OEM parts so they can be compared. We know that pin will be fat, but I think that is something being worked on.

 

[Lakeside53]

We know that pin will be fat, but I think that is something being worked on.

Why do you think that?

 

[blsnelling]

Could you include the weights of the OEM parts so they can be compared. We know that pin will be fat, but I think that is something being worked on.

That's my intentions. I just reuse the factory pin though, so it's a non-issue to me.

 

[stihl only]

Why do you think that?

Fat, as in HEAVY, not fat, as in diameter.

 

[Lakeside53]

Why do you think Baileys is working on that?

 

[Haywire Haywood]

Don't toss anything... test it un-ported as it came in the kit. If it fails, it fails and is then shown as a weakness. Unless of course, you paid for the P&C or are keeping it after the testing is done and would like to minimize the chance that something catastrophic happens. I doubt anything will happen anyway, at least in a short term test. Long term might be another story though. Yank it apart and replace the suspect bits and pieces afterward.

JMO,
Ian

 

[Lakeside53]

That's my intentions. I just reuse the factory pin though, so it's a non-issue to me.

Doesn't help the guy with a toasted pin though...

Did they send you a new coated metal cylinder base gasket?

 

[serial killer]

So with this kit, I'll be able to go longer before emptying my ashtray?

 

[nitro]

036 bb?

wonder if they got for the 036 ,but i just rebuilt mine so next time i would go big say-la-vee

when i do car or bike motors i weigh all the pistons and rods with a digital scale and match them to the lightest one

 

[forestryworks]

So with this kit, I'll be able to go longer before emptying my ashtray?

depends on how much you cut and how much you smoke