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Topics - JParty

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CB350/400 / Valve cover leaking

« on: July 24, 2021, 06:41:26 PM »

Hello,

I know this is a highly covered topic on forums, but I want to ask for specific advice regarding the o ring like valve cover gasket on the CB400F

Prior to a rebuild, I have oil coming out of this gasket causing a fair amount of oil smoke and mess. When I pulled the gasket off it was flat and looked quite old. I installed a new gasket from an aftermarket gasket set

I still have plenty of oil coming from the top end here. I also get lots of oil smoke as the oil burns off (you can see it bubbling on the top fin) which doesn’t inspire much confidence from me or other motorists (aside from making a mess).

I’m guessing this suggests I need to deck the head and top valve cover as they must be warped. However I really want to use this bike before the weather turns so I was wondering if any of you have found any other solutions.

For reference, I lightly oiled the o ring type gasket and followed the torque down procedure in the manual supplement. I wasn’t sure if I should pack anything in with the gasket but couldn’t see any mention so didn’t.

Thanks for your help,
Jaden

CB350/400 / Master cylinder bleeding

« on: July 17, 2021, 01:53:52 PM »

Hello,

This one is really doing my head in. I’m trying to bleed my brakes after restoration (so there is no fluid inside at all). I was originally trying to bleed them assembled, but have now taken the master cylinder off to try and bleed it separately.

What I’m noticing is that on depressing the lever, fluid moves around in the reservoir, but only a mix of air with a very small amount of brake fluid comes out. I have checked that both ports in the bottom of the master cylinder is clear, and cleaned the very small orifice with guitar string. I’m also noticing that the brake rod isn’t returning after depressing the lever. If I cover the outlet with my finger whilst pulling the rod back, I feel it pull vacuum on my finger, but it isn’t pulling fluid through the reservoir hole.

I’ve pushed on the outlet side with a blunt rod and it all seems free moving.

Any ideas?

I’m inclined to buy a whole new aftermarket master cylinder as these rival the price of a rebuild kit. Would like your thoughts for any with experience!

Thanks for your time!

CB350/400 / Rear swing arm bush

« on: June 01, 2021, 07:42:22 PM »

Hello!

I’m having great difficult removing the bushes housed in the rear swingarm that isolate the lower shock mount. I’ve tried pressing inside a vice and these bushes are properly stuck. Does anyone have experience getting these out? I don’t have a torch but I guess heat is the next and last option.

Thanks!

CB350/400 / Steering Tapered Roller Bearings

« on: May 27, 2021, 11:34:56 AM »

Hello,

I bought a set of tapered roller bearings from DSS. They look like they use QMP SSH 750 from the packaging. They didn’t come with instructions but after calling they issued a short document to me. The main thing I was unclear on was where the spacer (washer) went. From the instructions it is meant to go over the stem first before the lower bearing. The ID of the spacer was too small for the stem so I have to file down the centre.

Having ensure the cups were properly seated and the washer and lower bearing were hard up against the stem I’ve now tried to assembly the stem into the frame. Only 1-2 turns of thread is available at the top when trying to get the top cap (the nut that is torqued with a C Spanner). Because of the ridges on the bottom side of the top cap, it is only possible to start this thread with the nut upside down. With this torqued there still isn’t enough thread to see it come up the other side of the nut. I can’t get the thread started with the top cap on the right side up. Even if I can get a machinist to machine off those ridges on the top cap it doesn’t get my many turns of thread.

After triple checking that the bearing cups are seated in the frame, I’m running out of ideas. As far as I know, the steering stem and frame headset are all original for the 1976 CB400F. I’m reluctant to remove the spacer as it looks like the lower yoke will start to get plenty snug on the bottom of the frame.

Lastly, I was surprised to see an absence of any dust/dirt caps to protect the bearings...

Any help would be mega - thank you!!

CB350/400 / CB400F - My first bike

« on: December 13, 2020, 02:15:58 PM »

Hi friends,

I am UK based and made my first post about my new CB400F here http://forums.sohc4.net/index.php/topic,184902.0.html I didn't realise there was a community a bit closer to home!

I have an oil leak from the rocker cover. Is there are recommended suppliers of the rubber gasket?

On the original post I showed that the engine had been previously chrome plated and painted black on the cylinders. The prep must not have been great (and the coverage suggests it was done within the frame). I'd like to remove this and I'm still undecided if I do this (after masking) with paint stripper, or whether I rig myself up a homemade soda blaster. Would appreciate your input!

Currently I have the engine out and will adjust valve clearances. I did a compression test and seemed decent. Is there any other 'health checks' I can do to be sure I'm not better waiting to tidy the engine externals when I've done a full strip. Ideally I avoid this as the engine runs well.