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 1976 bonneville 750 rear brake maser cylinder
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bonnevillepatx

11 Posts

Posted - 08/16/2006 :  19:09:12  Show Profile  Reply with Quote
Hello I am brand new here. thanks for your help with the kill switch. Now on to the rear master cylinder for my newly acquired '76 bonneville 750. To start wtih the rear brake assy is in a box. The previous owner did a very good job putting the bike back together he just ran out of steam and sold it lucky me. ON my master cylinder. someone drilled out the set screw that sets the aluminum base bit with the stainless steel end piece. Well this someone drilled all the way through the set screw and through the stainless bit as well.
MY question is does brake fluid make it this far up the system? The hole in the stainless bit is on the set screw flat section. From the looks of it this is past the last seal on the piston. In what I would guess may be a dry part of the brake system???
If this is "wet" at this point. I will weld shut the hole and will rebore the ID of the stainless piece. When I put the master back together the aluminum base screws almost all the way to the end of the threads on the stainless part. Is there a sealant that goes on the threads??
thanks
bonnevillepatx

JubeePrince

USA
848 Posts

Posted - 08/16/2006 :  21:51:38  Show Profile  Reply with Quote
I would figure out a way to plug that hole..... some JB Weld would probably work nicely.....you could leave it, because I do believe that it is outside the throw of the piston, but it'd be a shame to put it together and then find out that's not the case......

You want to be sure upon reinstallation that you have the proper clearance on your operating rod adjustment......it's kind of important if you want to stop!!

Cheers,

Steve Prince

'77 T140J
That's not vibration......that's character!

"The paying customer is always right."
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tangerine-jack

USA
709 Posts

Posted - 08/16/2006 :  22:08:14  Show Profile  Visit tangerine-jack's Homepage  Reply with Quote
I would be very tempted to use that master cylinder as a wall ornament in the garage and not trust my safety to it. There is a thing called "ruined" that sometimes happens to parts over the long harsh years. No need to get upset, it's a fact of life for old bikes. My recommendation is to give that master cylinder a dignified little funeral in the back yard and order a new part.

Maybe you can repair the damage, maybe not. I have a strict, no compromise personal policy when it comes to safety so I wouldn't use a "maybe" part when a good, safe replacement is available.

Just my $.02

Words are so unnecessary!





Edited by - tangerine-jack on 08/16/2006 22:11:15
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bonnevillepatx

11 Posts

Posted - 08/17/2006 :  01:03:51  Show Profile  Reply with Quote
Hello thanks for the reply's. With the utmost; UTMOST respect ,Yes in this particular case new would be preferred. Please do tell where this part would be available. I called 'BO and there was no answer. I called MOore's, they say back order maybe not available. The PO provided the one he bought off ebay and it is a piece of crap, it will require more work than the original. Also it is very expensive in the catalog on the order of $80 to $140 if my research is correct. I am mig, tig(300 miles away), & bridgeport mill equipped. This does not seem to be that big a deal. especially if there is no high pressure fluid present in the area. I would be more than happy to buy a new stainless bit if I can find one, as this one is going to be questionable to seal up the hose barb bit on the top. Well in conclusion if I could get a new stainless steel bit I would go for that.
any help would be appreciated
thanks
bonnevillepatx
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Woody

USA
86 Posts

Posted - 08/17/2006 :  06:23:24  Show Profile  Reply with Quote
Bonneville,

you will have to search for and purchase the part number via BO web site. They aren't taking phone orders at this time.

Woody

77 T140v
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tangerine-jack

USA
709 Posts

Posted - 08/17/2006 :  07:06:26  Show Profile  Visit tangerine-jack's Homepage  Reply with Quote
email me off-forum and I will provide you some links to other suppliers. $80-$140 doesn't seem too bad a price to pay to be absolutly sure of safety.

OTOH, you have nothing to loose by trying to weld/drill and tap the part, if you are sucessful then please post a "how to" with photos and we can all learn from your efforts. If you fail, then at least you had a little fun and the part is no worse off than before.

CAVEAT: This is YOUR bike and YOUR project, in the end it's your decision how to proceed with whatever aspect of the job you are doing. Good luck, and please take all these posts in the helpful and friendly spirit they are intended.

Words are so unnecessary!




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JubeePrince

USA
848 Posts

Posted - 08/17/2006 :  08:18:01  Show Profile  Reply with Quote
Just for clarification..........the steel part that needs to be welded does NOT need to be drilled or tapped......

The aluminum housing would need to be tapped for the new grub screw.....

T.J. does have a good point......small price to pay for safety.....

Part # for the MC body only is 99-7027.

B.O. has it for 49.00.....but you need to order over the web and you need a minimum 150.00 order.....so get that bits list together....

You do have a parts book and factory manual, right?

Cheers,

Steve Prince

'77 T140J
That's not vibration......that's character!

"The paying customer is always right."
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bonnevillepatx

11 Posts

Posted - 08/17/2006 :  10:56:35  Show Profile  Reply with Quote
Hello and thanks for your help and opinions. Yes I do have a factory service and parts manuals, haynes manual, as well as moore's and BO catalog. I am still new at these two catalogs. The BO catalog is pretty confusing to me still. I just now found the 99# parts, in the BO catalog. The parrt discussd above is on page 197 in my catalog it is listed as 01-99-7027 in my catalog the 99 has a strike going through the print. Are we on the same page and part?
I would definitly buy a new one for $40. To repair this bit will probably take me several, several very hot and sweaty hours in the shop.
Well I am not sure what else I really need at this point. I was going to buy a bunch of new parts for this bike. But everything I thought was broken or difficult has been pretty easy. With the exception of the front RH handle bar switch and the rear brake bit as discussed. There are of coarse lots of little nick nacks I would like , but they are not just super necessary. The mufflers have a few months or good riding left in them. The reserve fuel petcock hadle is missing, the air filters are a bit old looking. My Mc rebuild kit should arrive today., I had to order it elsewhere as I got no response on the phone from BO.
I guess the short version is I do not have a $150 order today, If I wanted to get another rebuild kit and a T-shirt, I would be getting close, and getting mufflers early would put me there I guess.

I do not suppose that some one wants to split an order with me.

Well this is getting long winded. I did see the master cylinder stainless piece on line for $40 something. If I had seen that a few days ago it would have been in my hand tomorrow.
thanks again for all your help.
I am sure I will be asking some more questions soon.
yall have a good day
bonnevillepatx
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