To All The Members: i need an help.

[Riccardo]

I have a problem:

15 days ago, after a small walk with mine 1000737 (engine 1000940), approximately 30 miles, and I have discovered oil traces on the front part of the cylinders, between the 2 and the 3, in the zone between the base and exhaust manifolds, where is the grey antivibration grommet.
I have cleaned up the oil with a specific product (at cold motor) and, after a week, I have tryed newly.
I have seen, after some miles, the oil emerges newly, in the lower part of the fins.
It is not easy to see from where the oil comes, because -walking- it goes on all the surface of the fins.
The gasket of the cylinders is perfect and dry and also the gasket of the head of the cylinders.
Probably of draft of a blowing that comes from the passage of the distribution chain, than warm it leaves to pass a small oil amount.
I think to a very very small sandcasting porosity of the fusion.
I think that the faster solution is that than to find of cylinders SANDCAST, in order then to try, in according to moment a repair (if possible) of mine.

Someone has of the cylinders sandcast for me, to sell?
Correct type for my engine number?
I would be truly pleasing to who could give a hand to me in order to resolve this probrem.
Thanks in advance.
To all.

[kenhan]

Hi, could be the small rubber seals (nickels) under the camtowers. There is four 10mm bolts that hide under the rubber seals to help tighten the cylinder and head together. If the seal is leaking, the oil will go down in the fins area of the head. Depending on which rubber seal is leaking, the oil will come from four possible places.

/Ken

[gane]

Also possible, weep from cam chain tensioner, either at gasket or from tensioner rod passage. Tip, locating oil leaks when oil is new & "clear" can be difficult, especially for those of us with "poor vision". Powdered deoderants & arisol foot sprays show "snail trails" which are much easier to read, & are easy to clean. Luck g

[Riccardo]

thanks Ken and Gane for you reply.

Ken, is possibile for you post a photo of the point that you tought?

Ciao

[kenhan]

Hi again,

I try to attach a file that shows everything you need. This is a cylinder head from a 1970 but should look almost the same as a sandcast head.
The camtower lays on its side to show the bottom part with one rubber still sticking to the tower, two other rubber seals are also shown on the head, One in its correct position and the other slightly beside the hole for the bolts. You can also see one of the bolts laying down on the photo. The bolt goes in the hole to help tighten cylinder and head. The rubber is sealing the oil from going down in the hole and out in the fins area.

Not easy to explain this, especially in another language than my own, hope the picture will tell more than the words. If this is the reason fror the leak, you have to pull the motor out of the frame, unscrew the camcover and dismount the camshaft and camtowers to be able to change the rubber seals.

/Ken

[Riccardo]

Ok Ken,
you was very exaustive.
Yes, i'll do an inspection before unassemble the engine ( very big work).
Thanks again.
Riccardo

[hondasan]

Other possible ares of leak are from the cam tower fixing bolts / studs -
- The four front studs are threaded in tapped holes which are not blind - if thread sealent is not used on the lower (cylinder head) end of these four studs, which secure the front of the cam bearing caps, oil can find its way down the threads and out of the engine. It is likely to show on the lower cylinder head fins, but of course can easily (in the wind) end up on the upper cylinder barrel fins at the front too.
- The other 8 cam tower bolts (4 for the rear cam bearing caps and 4 for the rocker shaft locations, are threaded into blind holes. If incorrect / too long bolts have been used, they can crack the underside of the casting at the bottom of the threaded holes, so allowing oil leakage - and to make matters worse, the rear bearing cap bolts are also a part of the cam shaft oil feed route, so there is oil pressure trying to get the oil out past any cracks (I only found this one via a restored K1 which had suffered this particular problem).
- And of course the front of the cam chain tunnel  -any barrel / head gasket face damage here can allow oil leakage. Given the narrowness of the gasket face here and the lack of the (fitted later by Honda) head / barrel securing bolt, I always use some extra "sealant" around the gasket in this region.

Just my further thoughts on this one - #5298 has now done 86,000 miles since the last head gasket change, and NO oil leaks.

Cheers - Chris R.

[Riccardo]

Hi Chris,

i'll do an inspection the next week to see the oil way (if possible).

But, with all probablity, i'll dismount the engine in the next winter.

I'll keep in my mind your suggestions about this problem.

Yes, i remember well: the sealant was't used during the engine assembling fase (in those points) and i think your thought very  possible.

My displeasure is unassemble the engine from the bike, i retain this a violence,  because when one bike is finished this is for me the end of mine efforts to met the max perfection that i (of course) can.

I'll update You and the SOOC about the repair operations.

Ciao.

Riccardo 

[harald]

I had a similar problem and after a long time I found out the oil  came from defect seals of the front forks which the wind blew on the engine fins when driving. Another possibility is cracks or a cast fault in the alunimum head.
Harald