400/4 Forks

[andut]

I had my first trip out on the 400/4 of 2016 a few days ago and I was quickly reminded that the front end does seem a bit under damped.  Noticed it on the first few post rebuild rides last year, but having never owned a 400 before, I'm not sure what's 'normal' ! 

The forks were rebuilt with the rest of the bike last year with the old springs and fresh 10wt oil, but there does seem to be a bit of bounce to the front end - should I be looking to move to 15wt oil, or trying more volume of exiting oil ? anything else to be checking ? 

Also noticed a very minor weep of oil from n/s drain bolt, which had that horrible stripping thread feel when I attempted to nip it up a bit, so I'm pondering if I going to be able to helicoil without a complete strip of that fork leg - I'm guessing I'll have to to make sure there's no swarf from drill / tap for the insert ?

Thoughts and advice welcomed !

Andy

[ColCB400 4]

It would seem logical to just add a little more oil to each leg, maybe an egg cup full and see how it feels, keep adding till it feels ok. At least this way you can leave the drain bolt alone.
If you put half a pint in and it still feels pants then go for a higher grade oil and see how that goes but maybe you should be ready to deal with the drain bolt. You should be able to take the bottom of the leg easy enough... swarf cant be good but probably wouldn't matter... but inevitably would lead to doubt.
Don't you knock the little tang off when helicoiling, don't want that sloshing about?

Just add some more oil, it will stiffen up.

[Chris400F]

The Honda Common Service Manual from the 80's talks about filling forks to a specified level (using an improvised 'dipstick') - I seem to remember the CB-1 NC27 I had was done that way.
I think the principle of operation means there needs to be room for oil to move around, so adding more may not be the answer, it may be a case of using a heavier grade.

As far as helicoiling goes I suspect you will remove the fork leg to drill it anyway, so dismantling would be very little extra work and would eliminate any chance of swarf from drilling inside the fork. It would also be far easier to work on without the weight and added length of the stanchion..

[gtmdriver]

Should you choose to risk it the recommended technique is to use grease on the drill bit to collect the swarf but I've never had much faith in this method. Personally I'd pull off the fork slider.

[Vital Spark]

If you do all your drilling/helicoiling then pour white spirit into filler plug on top of leg won't this flush out any swarf? - hence no need to dismantle anything - shake forks while draining - or did I spend too long in NZ where thinking outside the box became normal??
Good luck from an old newbie.

[Bryanj]

Did loads of spark plug helicoils with lots of grease on the drill and tap and great care with the tang, never had a problem

[Lynx]

15wt Fork oil worked well in mine.