Topic: Oil leak from under cyliner head.

[Steve]

I have a problem with an oil leak from under the cylinder head on my 400/4 

Looking through the manual it looks like the seal of gasket around the oil orifice has failed between the barells and the head.

Can any one send photo of the the little sucker, has anyone bought a full engine set of gasket's for Dave Silver's and they included??

Any good idea's on how to solve the problem.

Looks like I have a stripdown job to do in the near future.

Thanks.

Steve (in the UK)

[bryanj]

Normally all the "O" rings are in a set and you will need a new head gasket anyway plus DSS has always been helpful to me and hios reputation is too good to risk selling crap

[Bodi]

The seal should be available separately from Honda, and is included in the top end gasket set (head gasket will be required as well anyway). I haven't ordered one in the last year or so but Honda Canada got me them about 2 years ago.
This leak is pretty much normal for 350-4 and 400F engines. If you're doing the cylinders I recommend having the cylinders and head machined flat as any warpage can make the leak pretty much impossible to eliminate. Putting a bit of hylomar or other gasket sealant around the oil orifice valve seals helps - but you have to be very careful not to overdo it and block the (vital) oil flow to the valvegear. You can look down from the top with the head on and see if the orifice looks clear after assembly.
I would stick with Honda gaskets. Athena supplies an orifice seal with a different profile than the Honda one, I've had both types leak after rebuilds.
Retorquing the head after a heat cycle uis supposed to help, I'm not convinced as I've had the leak re-appear either immediately or after a few hours whether it's retorqued or not. The high pressure oil gallery below the orifice is just too close to the edge IMO. You can just jam some paper towel between the fins to soak up the seepage and change it every week or so, keeps the engine (and your pants) clean at least.

[mcpuffett]

Hi Steve, i have just bought a complete gasket and o ring set for my 750 , i only had to order 4 seperate o rings,  3 for the oil pump and 1 for the main oil gallery this was from dave silvers , cheers mick.

[Zane]

I’m having the same problem - an oil leak.

I see where David Silver sells two top end gasket sets - one under “original” equipment - which I’m assuming is a Honda part.  They sell a second set under “pattern” parts, which might be an aftermarket brand, like Vesrah.  Does anyone know for sure if DSS’s “original” top end kit and/or separate gaskets under “original” are true Honda parts?

(I need to email them anyway, sometime soon, so if no-one knows, I’ll just ask them directly.)

Even with all the advice on this site regarding this problem with 400/4’s leaking oil, I’m still not too sure how to proceed. 

Does anyone know what the minimum is I need to do to re-torque the engine bolts (gasket wise)?  Like, do I need to remove the cylinder head cover only, or do I need to remove the entire cylinder head?  I’m somewhat intimidated by the whole process of dismantling even part of the motor, so simple answers (if there are any) would be appreciated at this end.

(And it sound like you've had poor results simply tightening the head bolts anyway, Bodi.  Maybe I'm considering the wrong approach here - I just don't know.  I don't want to spend bucks on gaskets, use them, and then find out I didn't fix the leak and that I need to get more gaskets right away because I've got to open the top end up again.)

[bryanj]

Honda do not recommend a re-torque but it is wise to make sure, when the head is off, that the nuts spin very freely on the studs and that the gasket surfaces are "Mirror Finish" clean, also that your torque wrench is accurate as the setting isnt high plus use the top setting.

[supersport_CB400F]

I’m having the same problem - an oil leak.

I see where David Silver sells two top end gasket sets - one under “original” equipment - which I’m assuming is a Honda part.  They sell a second set under “pattern” parts, which might be an aftermarket brand, like Vesrah.  Does anyone know for sure if DSS’s “original” top end kit and/or separate gaskets under “original” are true Honda parts?

(I need to email them anyway, sometime soon, so if no-one knows, I’ll just ask them directly.)

Even with all the advice on this site regarding this problem with 400/4’s leaking oil, I’m still not too sure how to proceed. 

Does anyone know what the minimum is I need to do to re-torque the engine bolts (gasket wise)?  Like, do I need to remove the cylinder head cover only, or do I need to remove the entire cylinder head?  I’m somewhat intimidated by the whole process of dismantling even part of the motor, so simple answers (if there are any) would be appreciated at this end.

(And it sound like you've had poor results simply tightening the head bolts anyway, Bodi.  Maybe I'm considering the wrong approach here - I just don't know.  I don't want to spend bucks on gaskets, use them, and then find out I didn't fix the leak and that I need to get more gaskets right away because I've got to open the top end up again.)

Zane, Honda gaskets are supplied from DSS and are top quality, just order genuine Honda parts they are listed on the web page under original parts not pattern parts, I’ve just used a full set on my engine rebuild, I did develop a small oil leak but not from the cylinder head and it was caused by my error not the part (nipped O ring in the oil pump).
Its not a complicated process taking the head off if you follow the instructions in a good workshop manual, I torque’d the head down several times during the time I was waiting to finish other pars of my bike and so far I’m pleased with all my Honda gaskets and rubber seals.

Cheers
Dave

[Steve]

Hi to you all

Thank you for the advice.

I have got a full set of gasket on the way from DSS, My plan is to do the job in May when the weather is warmer, and to replace the exhaust at the same time, just need to take out a mortgage to pay for it, have you noticed how much they have gone up at DSS.

Steve

[supersport_CB400F]

Hi to you all

Thank you for the advice.

I have got a full set of gasket on the way from DSS, My plan is to do the job in May when the weather is warmer, and to replace the exhaust at the same time, just need to take out a mortgage to pay for it, have you noticed how much they have gone up at DSS.

Steve

Be grateful you don’t live in the US you should look what they pay for a new set of pipes on ebay….scary!!!

[Zane]

Thanks biffta and all .....  although I'd still like to know where those engine bolts are located, that we're talking about.  (The ones that squeeze together the leaky joints.  Are they under the head cover only, or do you have to take off the whole cylinder head?  I can't tell from the pictures I have.  Maybe I haven't looked hard enough??)

The DSS prices seem excellent, actually.  Unfortunately for us New World folk - the shipping costs can be a bit much however.

But it doesn't take long to save shipping costs when a DSS 400F stock air filter costs almost $40.00 (CAN) less, buying from them instead of from Honda Canada.

I emailed DSS about shipping costs for two complete sets of spokes, a brake line pipe, and a couple of caliper bolts.  A little more than $20.00 - which really isn't too awfully bad, actually.  That still puts the spokes significantly less expensive than I can find anywhere on this continent.

I wish I knew a pilot or flight attendant that went between Toronto and London regularly, and who was willing to ferry back 400/4 parts. 

[supersport_CB400F]

Thanks biffta and all .....  although I'd still like to know where those engine bolts are located, that we're talking about.  (The ones that squeeze together the leaky joints.  Are they under the head cover only, or do you have to take off the whole cylinder head?  I can't tell from the pictures I have.  Maybe I haven't looked hard enough??)

The DSS prices seem excellent, actually.  Unfortunately for us New World folk - the shipping costs can be a bit much however.

But it doesn't take long to save shipping costs when a DSS 400F stock air filter costs almost $40.00 (CAN) less, buying from them instead of from Honda Canada.

I emailed DSS about shipping costs for two complete sets of spokes, a brake line pipe, and a couple of caliper bolts.  A little more than $20.00 - which really isn't too awfully bad, actually.  That still puts the spokes significantly less expensive than I can find anywhere on this continent.

I wish I knew a pilot or flight attendant that went between Toronto and London regularly, and who was willing to ferry back 400/4 parts. 

I’ll keep it short Zane it’s late, I’ve marked the oil restrictors points that cause the leak it has two one each side of the engine and they have O rings and they get hot and cold and deform and weep. If you need more information let me know.

Cheers

[Bodi]

The bolts to be retorqued are really the studs. You just have to pull the rocker cover off although the centre nuts are a bit tricky to get at in frame it's not hard. Luckily the 400F frame allows rocker removal without dropping the engine.
Get replacement sealing washers for the exposed studs - might be included in the top end gasket set - the old ones will be toast.

[Zane]

Wow!  I'm impressed.

Thanks biffta and Bodi.  ...... a picture's worth a thousand words.

I will get in touch Bodi, once I get into it.

By the way Bodi, where do you take your motor to have those surfaces machined perfectly flat?  Since we're in the same town, it's probably worthwhile for me to know.

[Steve]

Thanks for the picture Biffta, I got the gasket set today under 24 hours delivery good old DSS, I think that I can identify the the 2 seals from the set.  I don't think to much of the design with that sharp lip top and bottom I can see how they leak, the hole will need to be very clean for the to seal properly.

Best regards

Steve.

[supersport_CB400F]

Thanks for the picture Biffta, I got the gasket set today under 24 hours delivery good old DSS, I think that I can identify the the 2 seals from the set.  I don't think to much of the design with that sharp lip top and bottom I can see how they leak, the hole will need to be very clean for the to seal properly.

Best regards

Steve.

Steve, also get a couple of the special washers that fit under the indicated bolts you will need them! They don't come with the gasket set.

Cheers
Dave