Head bolts

[billbofagends]

OK, not firestorm related but I'm hoping someone has a cunning idea how to remove the head nuts on my Honda Benly and still have a usable engine afterwards. The pesky nuts holding the head and barrel together are seized on to the studs so when I turn them it unwinds the stud from the crankcase and not in a good a way but a very tight way that feels like threads in alloy are being stripped. I've tried obvious stuff so far - soaking in GT85 and applying heat to the nut but no luck. The plan was to put higher compression pistons in and I've taken the engine out the frame especially.

[vtrbarmy]

Have you tried an impact driver with a socket on - sometimes that can just be enough to break the seal between nut and bolt.

[warby221]

Don’t piss about with them get a nut splitter on the nut if you can?

If the threads are failing in the barrels and you over do them you’ll have a nice bit of scrap to weigh in



Any good garage should have a hydraulic splitter shouldn’t cost more than £30 just make sure to tell them not to try and undo them with a windy gun or braker bar or they’ll pull the threads out of the barrel
ps the pic is just one type of splitter there are others that look like G clamps and would fit over the top of the nut if space is tight

[benny hedges]

you could pack the area with bog roll to keep swarf away and drill the nut either side with a 1-2mm drill to weaken it, then when you put a socket on it will deform & come off easy.
get someone to hold a hoover nozzle close to the drillbit to get rid of crap & obviously be carefull not to damage the stud.

instead of trying to shock it downwards, sometimes a single sharp sideways tap will free it off the head, but you might find the entire stud comes out complete with the nut, in which case either grip it in a vice to free it off or use 2 nuts on the bottom of the stud.

nut splitters are great but you don't always have enough room to get them in, especially on the middle nuts

[billbofagends]

Problem solved...

Took a bit of a gamble and put a bit more force on the spanner and all the nuts cracked off fine. I think as the studs are so long, they can twist giving the appearance that the stud is winding out. Everything seems in tact so onwards with the CD185 pistons going in. New piston rings or use the old ones? The rings are the expensive bit at twice the price of the pistons!

[Twinpotter]

Cool, a Benly!
Used to have the CM200 Custom as a working backup, they're wicket wee blocks.
If the ring end gaps are within tolerances by all means reuse them, otherwise grab some new ones and fit a new head gasket. While the head is off, I'd personally check/replace the valve guides (a fiver each) and grind the valve seats back in - hopefully I'm no teachin you how to suck eggs but you'll need a valve spring compressor, a double sucker-ended valve grinding tool and some paste, all for about £30.
Go on, treat the auld lassie.
Good luck.

[AMCQ46]

I like it

What you doing with the rest of the bike, keeping standard or making a mini cafe racer?

[billbofagends]

Think I'm going to keep the rest of the bike standard, quite like the way it looks and it is very comfortable. Just needs that bit more power to make it usable in modern traffic. I attacked the head with a die grinder this afternoon, not sure if it will be worth the effort and time but it had to be done.

I need a bigger carb - does anyone know of a carb that has an OD of 34~35mm? I've got the intake manifold from a CM250 on the way over from the US which has a rubber inlet which is bigger than the standard. Plan was to use the CM250's carb but they are mega bucks for some reason.

[billbofagends]

Pistons in, engine loosely rebuilt, turn it over by hand and uh oh... its gone solid - piston is hitting the head! Cack, that wasn't part of the plan. So erm angle grinder to the top of the pistons? lol

[tony.mon]

Thicker cylinder base gasket, just an aluminium spacer using a head gasket as a template. Make sure you have enough cam chain slack.
You need about 0.6mm gap at least to allow for a tiny bit of crank and rod flex, and different rates of expansion.

But you might need to use octane booster if it;s really high comp, and think about how the plugs run, you could need a different heat range spark plug.

[billbofagends]

tony, aluminium spacer - you are a genius.

I was thinking 2 head gaskets together but it didn't look too clever. Think I need to stick an old piston in first to see how much that protrudes from the cylinder(I'm guessing nothing), that will give me an idea of how thick the spacer needs to be.

I've not tried this before, does it have to be a special grade or anything like that?

[tony.mon]

No, anything flat will do, it's shielded from the combustion gases and heat as the cylinder liner protrudes down lower that the base gasket.

If it was top end, head gasket, you would have to think about burning and heat transfer, but with the base gasket you're ok.

[billbofagends]

yeah, may have fooked this up spectacularly. spacer is a no go as this isn't enough cam chain slack. also, since the deglazing the pistons seem far too sloppy in the bore, distinct possibility I may have taken too much material out. So erm, shite. Probs gona need a rebore now and a of set o/s pistons just to get it back to standard.

[AMCQ46]

thats a bit of a bugger on both counts.

like your honesty in telling us you may have cocked up, I am sure the pisstaking will start soon though but like most of us, sometimes you can only tell when you have crossed the line when it is viewed from the otherside

PS, what did you deglaze the bores / pistons with.........., suggest you dont use that when polishing the bike!

[billbofagends]

Twas a proper tool, but a cheap draper one off ebay. Its the 3 legged type with stones. I need to get a dial gauge to measure the bores properly though as I'm only going on what it looks like, haynes book doesn't give the actual clearances. At least I still have the firestorm to play with still. lol