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Closing crankcases.
Posted: 16 Dec 2018 21:03
by Tim Louth
Hi all, planning on closing the crankcases of my 1982 350 Sport tomorrow and I have a couple of questions. What is the purpose of the neoprene rubber seal between the crankcases? It is around 10 mm long and 10 mm in diameter.One of the crankcase bolts go through it so it can't be for oil transfer. Secondly, 2 of the crankcase bolts are internal and have a copper washer on one end. Why is there not a copper washer on both ends if it needs to be sealed against leaks?
Re: Closing crankcases.
Posted: 16 Dec 2018 22:02
by EVguru
Look at page 124 of the Blue book. Most of the case bolts are outside the case joint line, but two are inside. One is at the back of the case, just below the kickstart shaft hole. The other is at the top, just behind the rear studs for the rear cylinder. This top one gets a lot of oil fling from the crank, so later engines used the same type of seal as the crank oil feed to improve the oil tightness of this joint. These two bolts are the ones with the copper washers. Since they go from the inside of the cases to the outside, even if the case halves are well sealed to each other around them, oil could creep down the side of the bolt, so the copper washer forms a extra seal under the head.
Re: Closing crankcases.
Posted: 16 Dec 2018 22:33
by Tim Louth
My copy has wiring diagrams on page 124.
Re: Closing crankcases.
Posted: 16 Dec 2018 22:39
by EVguru
Sorry, figures 123 and 125 on pages 72 and 72.1.
Re: Closing crankcases.
Posted: 16 Dec 2018 22:46
by Tim Louth
Thank you.
Re: Closing crankcases.
Posted: 20 Dec 2018 08:48
by 3potjohn
I had my 350K apart about 11 years ago and didn't appreciate the significance of the copper washers, result was an oil leak (not up to T160 standards but annoying nevertheless) After fixing this I had a tiny weep from the top of the crankcase joint around where the clutch lever passes. This time when rebuilding I checked that area of the faces very carefully as they were coming together, and used a very thin smear of threebond. No more leak. I also tried fitting the clutch /oil pump case with no gasket material and this leaked at the top joint near the pickup so I have used threebond again here. Very thin smear.
You may not have such troubles of course.
John
Re: Closing crankcases.
Posted: 20 Dec 2018 11:48
by Tim Louth
Thank you John.
Definitely a change from the Japanese bikes I am used to.
Not sure the what the Italians were thinking, or drinking, when they designed this engine.
Re: Closing crankcases.
Posted: 21 Dec 2018 19:14
by SupermotoDave
Not sure people here will be happy with criticism of “the engineer”
Re: Closing crankcases.
Posted: 21 Dec 2018 19:25
by 72degrees
SupermotoDave wrote:Not sure people here will be happy with criticism of “the engineer”
Absolutely - burn the heretic!
Re: Closing crankcases.
Posted: 21 Dec 2018 20:10
by Tim Louth
And who is this mystic 'engineer' I ask.
Is he related to obi wonky nobi?
Re: Closing crankcases.
Posted: 22 Dec 2018 07:08
by 3potjohn