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Discussion Starter · #1 ·
A second attempt at for this post, the last got well and truly Fubared (but me) posting wrong info.

Any how a quick recap, basically my engine is down on compression, 125psi when it should be 180psi.
Looked at stripping it before but cam to a halt as two of the eight head bolts would not come undone due to corrosion The two that were corroded were the inner two on the r/h pot.
Decided to drill the heads of as a hacksaw and grinding was a no no for obvious reasons. So engine out top cover off and ready to go.
I used an old bolt with a 14mm hex head, and cut the head off, faced up in a lathe and 4mm hole drilled in the centre. Put my 'jig' in a socket then over the head bolt. First covered the exposed rockers and cam with an old towel with a hole cut in it. I also have a huge magnet with a hole in, wrapped this in a plastic bag and placed over the head bolt. Drilled through my "Jig" with a 4mm drill to just over the thickness of the head bolt, the opened up to 7mm then a 10mm. Put a 14mm socked on the head bolt and it just popped off. Head cam off fairley easy but now the barrels are proving troublesome t move. Will apply a little heat tomorrow and hopefully get them off.

Pictures below.
 

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Good thinking about the pilot, had to do that for some sheared carb screws, will at some point have to do similar for some c/case head bolt holes for re threading, still saving hard for time sert set.

See CMSNL.com for the cylinder to c/case dowel positions. Find the reinforced areas for pry points but be warned, the c/case is thin in areas, so spread the load of the pivot point.

Wood protection for the fins is needed along with a good mallet. Perhaps fashion some suitable hard wood to fit between upper fins to make a broad punch......?

Don't forget your please God's...

Pictures and feedback to help others...

Unfortunately the 250 big end eyes will not pass through the cylinder bores. I will have to check but the rods and pistons will not clear the c/case internals even with the crank etc. out.

So it's cylinders off....

How is the balance shaft DOT etc. ?

Dd23
 

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Discussion Starter · #3 ·
When you drill the heads off use good engineering drill like Dormer. I used what i had and it was a gritty cut, called my mate and he came round with his Dormer drill, got a great curly swarf but. I also use Rolco cutting compound, it's generally use for tapping but was perfect for drilling the heads off.

I have been trying to knock the barrels loose with a wood block but no movement yet. I also used a Turbo Torch with Mapp gas just to warm the joint up but still stuck firm. Loathe to use hardwood as the fins may snap off.
I was going to post here about other ways to free the barrely. I did think about leverage but that does not sit right with me, yes i'm sure the crankcases are around 3 to 4mm thick and will not put up the a lot of pressure.

Have not looked at the balance shaft at all, want to keep side covers on till the barrels are free.

I have worked on many many bikes in the past and never had one like this.
One other little wrinkle, the top engine mounting bolt is also corroded solid in the alloy crankcase, I have not tried to remove it yet but will try the Turbo Torch first if not make a press type tool where i can wind a bolt into the corroded one, it will fit at the other end of the bolt so will only work against itself.
 

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The hard wood suggestion, a broad "punch" or drift that fits between the fins to contact the cylinder between the fins...

Find the dowel positions on CMSNL...the oe cylinder base gasket was green and had heat activated adhesive on the rear outer head bolt areas....they can be a bugger to "tear" to release the gaskets grip...

Much crap in the cylinder base holes where the now headless bolts live ?

Dd23
 

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Discussion Starter · #5 ·
The hard wood suggestion, a broad "punch" or drift that fits between the fins to contact the cylinder between the fins...

Find the dowel positions on CMSNL...the oe cylinder base gasket was green and had heat activated adhesive on the rear outer head bolt areas....they can be a bugger to "tear" to release the gaskets grip...

Much crap in the cylinder base holes where the now headless bolts live ?

Dd23
The other six bolts came out a little corroded and they have 'plastic ferrule's' on them. Good point on CMSNL and looking where the dowels are located.
I think it's just to cold at the moment and that gasket is really cooked on. Appreciate the idea about using a metal punch between the fins but it does not sit right with me. The shock mat transmit to the liner and possible crack it.
Didn't know about the heat activation on the gasket though.
 

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WOOD punch not metal !

If the hard wood is fettled to fit between the fins and is wide....to spread the impact area...horizontally...on the alloy casting that the liner is shrink fit...into.

You don't have to hit it hard enough to crack anything...

Two head bolts, front and rear left central have built on rubber seals, you will see why when the cylinder is off .

Another bit of brilliant honda design.

We are talking about the 6 valve engine here, 3 valves per cylinder, correct ?

If the pistons are at BDC, two good fit round bits of wood of sufficient length to form "levers", you have found the dowel locations, yes ?
 

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Discussion Starter · #7 · (Edited)
lol lol yea worked it out after i sent the message. I will have a look at what hard wood i have and will cut the slots on the bandsaw.

Yes 6 valve engine ;)

I like the other idea as well about pistons at BDC and a long lever square of wood. Actually got the perfect size in the garage.
 
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