Honda-SOHC

Andy,. Give the valve and seat a good clean and polish.  I use a cotton bud and a bit of Solvol to get the seat clean.


Andy

Ideally it's head off and a Wurth Time Sert, but they're not a cheap kit, plus new head gasket etc.  Faced with a similar problem a few years ago, I tried a Vcoil repair kit (Helicoil copy) without removing the head and all is well a few hundred miles later.  Obviously a risk with  cutting a thread without removing the head and potential to wind the insert out when removing the plug, but my experience has been good so far.

Andy

I'd recommend that you try using the original needle valves.  Just give the needles and the seats a bit of a polish and replace all of the o rings and then take some time to make sure that you get the float heights correct. 

Whilst you're in there, it's also worth checking that the jet sizes are std to get an idea if someone has been in there before you in which case you might want to think about checking needle heights.

Also check that both jets and the emulsion tubes are clear - make sure you check the cross drillings in the idle jets and the emulsion tubes. 

The choke flaps are simple to adjust to make sure that they're all fully open.

And as Julie mentioned, buy yourself a helicoil kit for the float bowl screws

Well done Dave, that's a great looking bike.  Whilst I hope the sun makes an appearance soon for you to get some miles on it, I also  hope you avoid the salty roads with all that shiny polished chrome !

Copper seems to be an out of favour head gasket material these days. More modern materials and manufacturing techniques have made other options more readily available for a lot of applications.  I have an old pushrod Ford engine in a Westfield that required a head rebuild a few years back, and I was advised by a very well respected engine builder to avoid replacing the copper gasket that had failed with a composite item.  Widely available for tunable car engines, but I'm guessing it would be more of a challenge to find similar for an old sohc honda as demand would be comparatively small.

There was a copper gasket on my 400 that was worked on by Dixon Racing back in the 80s, but it was no thicker than a std  gasket, so a Cruzinimage gasket has gone back on - will see how that goes !

Thanks for the great comments

Nice bike, where did you get the tank painted?

Tank was painted by a friend who happens to run a body shop in Essex. He's not a bike specialist, but did a great job on the tank and side covers - matched the original paint to something based on a Ferrari paint apparently so that's got to make it a bit faster and if it appreciates anything like a 40 year old Ferrari, I'll be retiring soon !

Looks very nice! My favorite color!

Dresda arm for sell?

Hi Emiel, sorry but the Dresda swinging arm was swapped with my other 400 that's a bit more 'cafe' so a bit more appropriate I thought.

Apparently there are far too few Parakeet Yellow 400’s around these days, so I’m happy to report that one more is now alive !

I know we love a pic, so here’s a snap of my recent project having completed a quick test ride at the weekend – I have since discovered a minor oil weep that I suspect is oil pressure switch related, and a brake fluid leak from around the lever that I’m hoping a repair kit will fix – lesson learned there as the master cylinder was the only part not stripped and rebuilt as it actually looked in good shape !

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I ‘accidentally’ bought the bike in boxes 18 months ago from a chap who was emigrating and I was very pleased to find a lot of the small, hard to get original parts were still in various boxes and bags.  It has/had a few period add-ons with a Dresda arm that has now been replaced with an original, a Cibie headlight and some engine work apparently carried out by Dixon racing in the 80’s comprising a Yoshi big bore kit and some head work.  On stripping the engine, I found the bores were heading towards the upper piston / bore clearance and borderline oval, so had to bite the bullet and get Cruzinimage’s 54.5mm pistons to give me a last chance oversize vs. Yoshi’s 54mm item – we’ll see how that goes, and I now have a spare set of std bore barrels as a fall back plan !

A quick thanks to Ken (Oddjob), Kev (fryerk) and to Graham & Julie who very kindly donated a few engine bolts, clips and oil galler caps to help me along the way.

Hoping to get the oil switch and master cylinder sorted and get a few miles on Peter (Kent400)’s shiny refurbed gauges before the weather changes – will also get a few nicer images to share !

That's a nice looking bike Graham, and a much better plan to build a bike rather than sell a collection of parts.  I'm sure building something different to the normal restoration will provide a different riding experience and that exhaust will release the inner hooligan