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If I recall from my other 850 top end 8 years ago, the cylinder base gasket goes on dry, correct? I have a gasket that looks like a paper material and is sort of flesh tone.
cylinder base gasket ?
- Thread starter britbike220
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A lot of people leave the base gasket out (i think all 750 had 'em -850 not not sure some techno-nazis will correct me) , i like having them in, though i prefer using the copper ones, and and have never had a problem with leaks. I use loctite 518 sealer rather than yamabond - the advantage of the copper ones - as explained in link below is you can also reduce your CR a tad and make the motor more fuel friendly
http://users.gotsky.com/jimschmidt/jsmo ... ession.asp
http://users.gotsky.com/jimschmidt/jsmo ... ession.asp
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I am trying to use the paper gasket I already have and just need to verify I can put it on dry because I'm pretty sure that's what I did before and have 0 leaks, thanks.
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mattfitz, thank you.
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Nothing wrong with using a base gasket or plate, AS long as you realize you must stay ahead of the crush and shift factors till settled down just like head gasket. Also if really wiping your hoss Norton, heck any BI engine becomes more rubber like at the seams so racers and hot riders usually seat barrels on case with just thread and sealer. Just NEVER use Al as the material. Factory tired that with bad results. Its a warning mentioned in the INOA Tech Notes. Always heat full bright cherry red any copper gasket and don't help it re-harden by fast water quench or much handling in its warm wax state. Some use metallic copper paint as gasket seal and of course there is the dedicated Copper Coat sealer.
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I am with Flo on this.
Just had an entire rebuild, and used a new base gasket and sealing compound.
You got only one shot to get a good seal there because you cannot re torque the through bolts.
No reason to take a chance of any leakage.
Just had an entire rebuild, and used a new base gasket and sealing compound.
You got only one shot to get a good seal there because you cannot re torque the through bolts.
No reason to take a chance of any leakage.
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The 850 didn't use a base gasket then it did. Norton found that folks were getting sealant goop in the oil passage drain from the rocker box so there is a tech bulletin re-instating the use of a gasket (no sealant) for the 850. I don't use a gasket on my 850 and if you are really careful with the sealant and ensure the passage is clear after bolting the barrel in place (pipe cleaners/solvent/compressed air) it's not an issue at all.
maylar
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The 73-74 parts book doesn't show one, and the 75 MKIII book does.. so I guess Mike's correct. As I said, keep any sealant very thin and stay away from the drain hole. I usually poke a heavy solid wire or threaded rod (6-32?) down the hole after snugging the cylinders just to be sure it's clear.
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I don't know weather or not the 73 was/is suppose to have one, but my first 73 had one when I bought it and I put one on it when I had the cylinder bored and have never had a leaky base or noticeable problems. I just don't want to have to take this thing apart again for awhile.
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I coulnd't find the Norton tech sheet that I was SURE I read re the use of the base gasket but I did find this quote out of the NORTON OWNERS club service notes:
"CYLINDER BASE GASKET: This was deleted from Mk. I and II 850, plastic gasket such as Loctite, Hermetite RTV or similar silicone compound being used. A gasket was again introduced, part no. 0638 12, on the Mk. III as people filled the oil drain with RTV, causing lots of trouble. Removing the gasket puts the compression ratio up by approx 0.3 of a ratio, see table. The 850 gasket can be used on the 750 but not vice versa as the cylinder apertures aren't big enough. 750 base gasket is part no. NM24249 or Q67869."
"CYLINDER BASE GASKET: This was deleted from Mk. I and II 850, plastic gasket such as Loctite, Hermetite RTV or similar silicone compound being used. A gasket was again introduced, part no. 0638 12, on the Mk. III as people filled the oil drain with RTV, causing lots of trouble. Removing the gasket puts the compression ratio up by approx 0.3 of a ratio, see table. The 850 gasket can be used on the 750 but not vice versa as the cylinder apertures aren't big enough. 750 base gasket is part no. NM24249 or Q67869."
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guess it sounds like personal preference, gasket, no gasket, copper, paper, paper w/goop, copper, copper w/goop and of course just different types goop.................Now if that wouldn't confuse a guy 
britbike220 said:guess it sounds like personal preference, gasket, no gasket, copper, paper, paper w/goop, copper, copper w/goop and of course just different types goop.................Now if that wouldn't confuse a guy
Got to get this in perspective - the Commando was designed for Sherlock Holmes.
Mick
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isn't dave suppose to chime in now with something about a picture :shock:
Why do I use gasket & wellseal?
Back in the days of yonder, I rebuilt my engine without a base gasket & just sealant. It leaked badly. So I took it apart & tried it again. It leaked again. So I took it apart again & used a mixture of red hermatite & wellseal. At last, the leak stopped.
So whenever the barrels come off, they go back on with a gasket & goo, don't want to put up with that again.
I always get the impression that the face that the barrels sit on are never that good on any bike & are not easy to lap flat.
Back in the days of yonder, I rebuilt my engine without a base gasket & just sealant. It leaked badly. So I took it apart & tried it again. It leaked again. So I took it apart again & used a mixture of red hermatite & wellseal. At last, the leak stopped.
So whenever the barrels come off, they go back on with a gasket & goo, don't want to put up with that again.
I always get the impression that the face that the barrels sit on are never that good on any bike & are not easy to lap flat.
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"Glad we settled the question of whether or not to use a base gasket!"
Yep, it is clear...use one! Or Don't!!
It seems clear to me that the factory had determined that a gasket was not needed as far as the engine was concerned. But field mechanics were gooping up the intake rocker box oil return so it was decided that it was better to have a (dry) gasket in place rather than a clogged return passage.
I agree that the mating surfaces don't appear all that true OTOH, at least on my 850, no gasket and Permatex Ultimate Gray Motoseal (with care re the oil passage) produces an oil tight seal and heck, I get that additional .3 increase in compression that Norton intended!
As noted, do whatever you want to do; the critical item is ensuring that oil passage is clear.
Yep, it is clear...use one! Or Don't!!
It seems clear to me that the factory had determined that a gasket was not needed as far as the engine was concerned. But field mechanics were gooping up the intake rocker box oil return so it was decided that it was better to have a (dry) gasket in place rather than a clogged return passage.
I agree that the mating surfaces don't appear all that true OTOH, at least on my 850, no gasket and Permatex Ultimate Gray Motoseal (with care re the oil passage) produces an oil tight seal and heck, I get that additional .3 increase in compression that Norton intended!
As noted, do whatever you want to do; the critical item is ensuring that oil passage is clear.
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