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Sealing compound for joining the crankcase halfs

Classic Norton Commando Motorcycles.

Re: Sealing compound for joining the crankcase halfs

Postby lcrken » Wed Jun 24, 2015 3:15 pm

Yamabond 4, Hondabond 4, and Threebond 1194 are all three pretty much the same sealant, and are pretty much the industry standard for sealing motorcycle crankcases. All three are the same synthetic rubber, semi-drying compound. I've used them for years on Norton and Yamaha crankcases. I also like the Hylomar Blue that hobot mentions. I use it a lot for general purpose mating surface sealing. It's pretty neat stuff, with a long history, starting with Rolls Royce. Google it if interested. I like that it is self-healing. You can remove a cover that was sealed with it, and replace it without cleaning or re-applying the sealant. Lots of other liquid gasket products out there that also work well.

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Re: Sealing compound for joining the crankcase halfs

Postby 84ok » Wed Jun 24, 2015 3:18 pm

Nater_Potater wrote:
hobot wrote:...might consider organic fiber thread laid in the seams as traditional on problematic aircoolled aricraft...

'Was taught in A&P school to lay #40 silk thread along seam after applying sealant to act as a "crush washer". It works well!

i woulda thought this ' #40 silk thread ' type deal would be fairly common here, i'd hafta dig but pretty sure that's what mercedes also does ..at least with some engines that have split (or 2 piece) upper & lower oil pan scenarios
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Re: Sealing compound for joining the crankcase halfs

Postby boz » Wed Jun 24, 2015 3:21 pm

Jim you probability can't find the Three Bond etc. in local shops because of the solvents. I remember about 10 years ago the original Yamabond disappeared because the EPA banned it.

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Re: Sealing compound for joining the crankcase halfs

Postby 84ok » Wed Jun 24, 2015 3:27 pm

http://www.aviationpros.com/article/103 ... o-disaster
The latest revision of Textron Lycoming Service Instruction No. 1125 specifies POB No. 4 Perfect Seal and silk thread as the generally used items for sealing crankcase finished parting surfaces that do not employ gaskets. Two other products, RTV-102 or LOCTITE-515 applied as a very thin film without silk thread, may be used as alternate materials for sealing crankcase parting surfaces. Other sealants have not been tested and approved for this purpose, and NONE are approved for other uses in the assembly of Lycoming engines. Improper use of these and other sealing compounds can create serious problems. As an example, a red colored sealant was used by a mechanic to hold the pressure screen gasket in place. As the material solidified, pieces broke loose and eventually blocked the engine's small oil passages causing oil starvation and engine failure. The bottom line: only use those sealant materials approved by the Lycoming Overhaul manual and other service publications, and only use them for approved purposes.
Last edited by 84ok on Wed Jun 24, 2015 3:34 pm, edited 1 time in total.
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Re: Sealing compound for joining the crankcase halfs

Postby concours » Wed Jun 24, 2015 3:29 pm

boz wrote:Jim you probability can't find the Three Bond etc. in local shops because of the solvents. I remember about 10 years ago the original Yamabond disappeared because the EPA banned it.


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Re: Sealing compound for joining the crankcase halfs

Postby comnoz » Wed Jun 24, 2015 3:39 pm

concours wrote:
boz wrote:Jim you probability can't find the Three Bond etc. in local shops because of the solvents. I remember about 10 years ago the original Yamabond disappeared because the EPA banned it.


https://www.rockymountainatvmc.com/p/30 ... sket-Maker


Yeah, but they have changed the formula [or at least the part number] and it's still available. The kids at the local Yamkawzuki shop didn't know what it was and the local Harley shop was out of it. Amazon got it to me fast. Jim
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Re: Sealing compound for joining the crankcase halfs

Postby acotrel » Wed Jun 24, 2015 4:11 pm

Thanks for the clue about using non-waxed dental floss. My crankcases always leak at the joint between the halves. This has given me another reason to strip the 850 motor and rebuild it with the combat cam.
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Re: Sealing compound for joining the crankcase halfs

Postby dennisgb » Wed Jun 24, 2015 5:05 pm

Nater_Potater wrote:
hobot wrote:...might consider organic fiber thread laid in the seams as traditional on problematic aircoolled aricraft...

'Was taught in A&P school to lay #40 silk thread along seam after applying sealant to act as a "crush washer". It works well!


This is the aircraft engine trick that Hobot was talking about. It is a very good solution for engine case halves.
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Re: Sealing compound for joining the crankcase halfs

Postby hobot » Wed Jun 24, 2015 9:02 pm

Just do NOT use the common synthetic threads as they melt and contract to leave voids in sealants so only real silk cotton, wool or hemp thread which is a bit pricy for the amount needed. Its tedious tricky to get thread to lay down and stay put to add sealant and clamp down. If an oil tight Commando is run in damp conditions or stored to open air the non SS parts of fasteners with rust to notice in about a season and have not found spray on that stays on engine fasteners beyond that. Prior I put light coat of blue snot on via Q-tip to press thread into and add layer over that but next time will coat tread in goop, let get tacky to stay down as its laid down and not disturb it adding the full dose. My favorite one goop seals everything head to tranny and home plumging projects costs more than $50 for 75 ml nowadays. I found some ancient mercerized cotton thread in my 95 yr old aunt Alice sewing kit on wooden spools to boot. I see cotton thread offered in http://www.deutscheoptik.com/ catalog for $9 a spool plus shipping and worth some window shopping or hard copy catalog of vintage and new craftsmanship items galore.

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Re: Sealing compound for joining the crankcase halfs

Postby JimNH » Mon Aug 31, 2015 1:16 pm

We used to have the thread in the shop with a Continental Motors P/N on the spool. I'm pretty sure it was silk.

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Re: Sealing compound for joining the crankcase halfs

Postby Torontonian » Mon Aug 31, 2015 1:24 pm

My next trip to Bangkok I will pick up a nice roll of natural uncoloured silk thread. PM me if you need any free , plus letter postage. This winter. :wink:
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Re: Sealing compound for joining the crankcase halfs

Postby toppy » Mon Aug 31, 2015 1:54 pm

Wellseal. It works fine an if it gets into oil ways the oil washes it away. If your joint faces are good then that is all you need.
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Re: Sealing compound for joining the crankcase halfs

Postby pete.v » Mon Aug 31, 2015 2:25 pm

I enjoyed success from Hylomar Universal Blue.
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Re: Sealing compound for joining the crankcase halfs

Postby JimNH » Mon Aug 31, 2015 8:32 pm

This is a list of TCM approved sealants, oils, etc. Near the end is an illustration of how to apply sealant and silk thread on crankcase halves.

http://www.tcmlink.com/pdf2/SIL99-2C.pdf

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Re: Sealing compound for joining the crankcase halfs

Postby Brooking 850 » Tue Sep 01, 2015 6:34 am

I use Loctite 515 , purple colour, for my cases.
Excellent results
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http://www.loctite.co.uk/sea/content_da ... _515EN.pdf
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