Re-Assembling Clamshell Engines?

[SteveSr]

Go to the local Yamaha/Honda dealer parts counter and get a tube of xxxBond4 for $10. I've never had an issue with it.

I also did some research on xxxxbond 4 and got some conflicting results:

Yamabond 4 -
https://www.shopyamaha.com/product/details/yamabond-4-motorsports?b=Search&d=36|36
This appears to be a gasket maker that will fill gaps. Not to be confused with Yamabond 4 Marine. No mention of fuel or oil resistance.

Hondabond 4 -
This is from a Honda tech bulletin. You can read the whole post here:
http://honda-tech.com/forums/tech-misc-15/knowing-hondabond-use-3188036/

"Hondabond 4 Semi-Drying Sealant P/N 08717-1194 - Liquid gasket sealant used to seal critical areas as specified in service manuals. Do not use it for gasketless applications."

This tells me that it is NOT a gap filler and never fully cures. This would appear to make it non-suitable for our saw applications. It would appear that the Hondabond 4 is similar to Motoseal.

I suspect that others who used Motoseal or Hondabond 4 didn't bother to pressure test their workmanship and probably got lucky. Given enough heat and time it may harden sufficiently so as not to blow out.

Based on this recent fiasco I am extremely hesitant to use anything except what Stihl recommends. I think I am going to bite the $$ bullet and order the Dirko. It is GUARANTEED to work.

 

[a. palmer jr.]

I've never had an issue with Motoseal, maybe you didn't put it on correctly. I make sure the mating surfaces are dry and clean then put a layer of Motoseal on both mating surfaces, let dry for a few minutes and then slap it together! Let it set overnight with the surfaces bolted together then remove the bolts the next day. It works somewhat like contact cement and I prefer it to Dirko. It's hard to get lucky as many of these engines I've put together...

 

[Chris-PA]

I suspect that others who used Motoseal or Hondabond 4 didn't bother to pressure test their workmanship and probably got lucky.

Yup, just a bunch of guys doing sloppy work that got lucky.

Yamabond4 and Hondabond4 are really ThreeBond 1184. I would have had to register to get the US datasheet, but here is one from the UK:

• High padding property, excellent sealing effect.
• Excellent resistance to vibration and impact.
• Forms a semi-drying rubber-like elastic body.
• Maintains stable properties from -40°C to +150°C.
• Excellent resistance to water, oil and gasoline.
• Applicable for threaded joints as well as flanges.
​

I've torn apart engines where I used it and never seen any sign of deterioration. Small drops and strings that got onto interior surfaces had to be scraped off.

 

[SteveSr]

I've never had an issue with Motoseal, maybe you didn't put it on correctly. I make sure the mating surfaces are dry and clean then put a layer of Motoseal on both mating surfaces, let dry for a few minutes and then slap it together! Let it set overnight with the surfaces bolted together then remove the bolts the next day. It works somewhat like contact cement and I prefer it to Dirko. It's hard to get lucky as many of these engines I've put together...

I think the key may have been waiting longer to let the stuff set up more before assembling. I followed the package directions which said to wait for 1 minute.

Given what I now know about these different sealing materials I would not use Motoseal because of it's non-drying nature and inability to fill gaps. It is clearly a different type of material than what Stihl decided to use. Stihl had their choice of many different types of sealers and picked the Dirko RTV type for a reason.

 

[a. palmer jr.]

Motoseal was designed for the same thing only for motorcycle engine halves. Of course the thicker you apply it the longer it takes to become tacky, the intent is to catch it between when it is wet and dry, not completely dry, as I stated earlier, kinda like contact cement. I've used Dirko before, have a tube of it right now and will eventually use it, it is somewhat thicker than Motoseal and isn't applied like Motoseal, I just put a coat on each surface and stick it together wet, the rest of the procedure is like Motoseal. Both work equally well when applied correctly, I just find Dirko a bit messier because it ends up on everything when I use it for some reason. I think I still have a shirt with Dirko on the front of it!

 

[Mattyo]

I just had a loctite 518 fail...metal to plastic is no go . ...

Trying 1184 as we speak

 

[SteveSr]

Yup, just a bunch of guys doing sloppy work that got lucky.

I think that I didn't make myself perfectly clear. I wasn't knocking anybody's workmanship, only the possible differences in procedure. Mine failed because I chose to pressure test the assembly which blew out the uncured sealant. Had I not done that the engine probably would have been fine and the sealant would have eventually cured overtime and operating temperature and I would have been none the wiser.

 

[ChoppyChoppy]

https://www.permatex.com/product-category/gasketing/anaerobic-gasket-makers-flange-sealants/

I've never had a problem. Comes out like real thick red loctite. smells good too.

 

[Mattyo]

VF, that stuff is likely similar to 515 or 518 loctite. I will have a vid soon that proves its no good for a metal/plastic union. metal metal is good though

to the OP, can you give pix as to what two pieces you are trying to put together? i'm unfamiliar with the stihl clamshell.

 

[SawTroll]

I recommend a sledgehammer and a dumpster for a 025 that is acting up - that's about how it is meant to be, they weren't meant to last or be repaired.

Then buy a proper saw from the same dealer that fooled you in the first place.

At least that's about how they want you to act, so don't fall into that trap!

 

[a. palmer jr.]

I don't know why an 025 wouldn't last a lifetime since they make every part on the saw aftermarket now. If a part goes bad just replace it, you can even buy a new aftermarket engine cradle for it now..

 

[SteveSr]

Here is the MSDS for the Threebond 1184. As you will notice it is solvent based.

Since the Dirko is an RTV product the equivalent Threebond product would likely be one of these 1200 series products...
http://threebond-europe.com/product/series/?series=3

Do any of these numbers sound familiar or are readily available? Any good sources for Threebond products?

 

[Matt_Ellerbee]

Subd.

Tackling a ms250 sometime next week. Doing all rubber parts and seals. Gonna have a nice little truck/Polaris ranger saw. Going to use locktite 515 as I have a tube already.

Any tips for pulling flywheel and clutch? Or just piston stop it,spin clutch off and flywheel nut and tap with hammer?

Well I have dove in!

Removed old gasket,cleaned. Replaced seals and set crank in place. Loctite 515 on one half,let set up for a few mins. Mated the halves,started all 4 bolts to be sure holes lined up,then clamped. Crank spins with no hard spots.

I'll know tomorrow if it worked!

And yes,I will be cleaning the case before tossing motor back in.

 

[a. palmer jr.]

Well I have dove in! Looks okay so far..

Removed old gasket,cleaned. Replaced seals and set crank in place. Loctite 515 on one half,let set up for a few mins. Mated the halves,started all 4 bolts to be sure holes lined up,then clamped. Crank spins with no hard spots.

I'll know tomorrow if it worked!

And yes,I will be cleaning the case before tossing motor back in.

 

[Matt_Ellerbee]

Got her back together and running.... till she died. Was letting it idle for about 30sec,then dead. Will not restart. Plug is wet. Damnit. But she ran!! I'll let sit and try again tomorrow. With bar and chain,so I can rev her some and adjust carb. Ugh.... I need a beer.

 

[Chris-PA]

Got her back together and running.... till she died. Was letting it idle for about 30sec,then dead. Will not restart. Plug is wet. Damnit. But she ran!! I'll let sit and try again tomorrow. With bar and chain,so I can rev her some and adjust carb. Ugh.... I need a beer.

You'll get it - that doesn't sound like it's related to sealing. And just for reference, other clamshells simpler than those things.

 

[Matt_Ellerbee]

You'll get it - that doesn't sound like it's related to sealing. And just for reference, other clamshells simpler than those things.

It was running before the teardown,with an air leak. I'm sure it's over fueled to compensate the extra air. I didn't even think to set carb to factory L/H settings. Live and learn,and I'm living and a learning!

And to anyone that is going to try a rebuild,do it! Sure,you'll learn some new cuss words at times,but the overall feeling is great! I am 100% stoked that it fired and ran on the 3rd-4th hard pull after a few easy ones to prime carb.

 

[a. palmer jr.]

I don't think those 250s are the worst either, I think any Echo saw is worse than a Stihl in almost any repair you do. The MS180 is probably a little worse than the 250 mainly because they're smaller. Most of the problems on the 250 are carb related once you get the engine sealed. I usually go on ebay and get a new replacement that is fully adjustable, many of the 250s I get aren't adjustable.

 

[Chris-PA]

I don't think those 250s are the worst either, I think any Echo saw is worse than a Stihl in almost any repair you do. The MS180 is probably a little worse than the 250 mainly because they're smaller.

My dad's MS250CM was certainly not a challenge to take apart, just pointlessly complex for no benefit (the definition of German engineering). That orange plastic part is an example of a design-for-manufacturing faux pas, with tubes connecting from all sides, especially with the purge bulb on his. At least it had copious amounts of molding flash that nobody had bother to remove, just like my Chinese clones.

 

[a. palmer jr.]

The 250 I use has the bulb but nothing is connected to it. I left the bulb there just to fill in the hole. When I changed carburetors I took off everything that wasn't necessary. My saw starts great without a prime.