Winter Work

[hondatri]

Hi I am back again I checked compression and got between 80 and 100psi Manual says 170psi so its more work than I thought. I am going to have engine rebored     I was thinking of just replacing rings but I think I will go the whole Hog. Bike has done 30K miles. I would like to thank Andrew for the very informative Manual he Emailed me. I have rebuilt a few Triumph engines in the past and would appreciate any Tips people have picked up in the past doing a 400 engine.

[Trigger]

The only real thing you must watch out for on the 400's is the cam chain tensioner. 30K seems a bit low for a compression problem but, you will not know until you get inside.

[Lobo]

Did you try a squirt of oil down the bores to check if the pressure 'recovers' on the compression test? If so, indeed likely the bores / rings, if it doesn't recover may be indicative of valve problems....

Simon

[Orcade-Ian]

Did you have the throttles wide open when you did the compression test?  It makes a big difference if they are shut, as the cylinder has difficulty gulping enough air to actually compress.
Also, my spare 350/4 engine - which I'm using in the bike at the moment - had less than normal compression and I glaze busted the bores and used the original rings.  It doesn't use oil and now has a healthy compression.  This was a stop gap measure until I get the original unit back in but it is absolutely fine - I was out on it yesterday. 
As some of the others say, the cam chain tensioner is the part to rectify - but they are easily repairable as outlined in my article in the VJMC magazine.  Also many folk don't remove the rotor from the crank, saying it's OK to lift out the crank with it attached.  I never do it that way as you cannot then renew the crank seal on that end - having spent all of that time and money on gaskets alone, you could be spoiling the ship.
I am writing an article as we speak for the VJMC mag on the rebuild with pics of my original engine, and it will appear in full form on my web site too.

Hope you get sorted with your winter work,
Ian

[AshimotoK0]

Keep it coming Ian (Orcadian) Sounds like you have got some good stuff to share with us there. Never joined the VJMC. Is it worthwhile doing so?
Anyone else got experience of being a member?

Cheers .. AshD

[Orcade-Ian]

Hi Ash,

I've been a member of the VJMC for a good number of years and met quite a few good friends along the way.  It's a matter of personal choice.  Writing an odd article also brings the benefit of a couple of months free membership and allows others to have the info - just the same as this excellent forum.  As you might glean from a quick look at my own site, I'm also into other bikes and cars and as a time served Aircraft Engineer with a well equipped workshop, I tackle most jobs deemed impossible (read too expensive) by the dealers and other 'experts' and usually try to engineer out some of the known weaknesses in designs by accountants when doing a rebuild.  Now retired and living in Orkney, I have more time to play!
Ian

[Lynx]

Hi Ash,
I've been a VJMC member since buying the 400 project bike a couple of years ago. I find the club magazine pretty boring, but you do get discount on bike insurance, some good stuff on the web site and details of local meets. Most regions meet once a month. However I'm in the The West Midlands who's VJMC club meet has folded up  . Is was in central Birmingham which wasn't ideal.

[UK Pete]

I went to a couple of vjmc meets, not really my cup of tea, i did not have a lot in common with any of them, i felt every one was old before their time, my problem is i still behave like i am in my 30's
pete

[hondatri]

 In reply to Orcadian No I did not open throttles when checking compression just fitted gauge and turned over motor nor did try oil in Barrels. I have the Rocker cover off at the moment and wont get near bike for a week But I will temporarily replace it and carry out test as suggested and will post results, Thanks for info.

[hondatri]

Hi me again I had low compression on test around 75psi as suggested I put oil in cyl and compression improved conciderably. I have removed head and barrels The pistons have no marking on top so are they standard (They are Honda pistons)  The Dia of pistons is  51'04 mm. I removed adjuster nut on front of engine and using a screw driver I checked the Horse Shoe for movement and it was very stiff to move I used a screw driver on the front and another at the back and rocked the horseshoe and it was stiff but moving . Should I rebore or would I get away with deglazing and new rings. I dont do much milelage,  Thanks for help and suggestions so far.

[Johnwebley]

I recently put new rings in my 500-4

 only £15 a bore,and de-glazed the bores using a long slitpin emery strips and electric drill,

the cylinders and rings bedded well

http://tcmlink.com/fiddefault.aspx?cgroup=MATTITUCK&cpagename=BREAKIN


 

[Lynx]

I'd just fit new rings and deglaze.

[hondatri]

Thanks Guys seeing that there are no marks on Piston Crown can I assume they are standard

[Bitsa (Ralph Wright - RIP)]

Crap Pete I have your problem except the bonce is 19 and the body 80
Crapper eh?
Cheers
Bitsa

[Clem2112]

I thought the Haynes book was ok, personally.

Be prepared to repair (helicoil) some of the tapped holes in the top of the head.
Last time I lifted the lid to check/torque the head bolts a few more threads let go when
I replaced the cam cover.
Using a genuine Honda head gasket is a good idea too.