Gen 1 engine rebuild

[huw s]

Hi all, newbie here. I have a Canadian import, triked with a sprung back end. The paperwork I got with it indicated it had been treated to all kinds of goodies - upgraded alternator, Barnett clutch, stage 1 jets, crankase vent kit, don't recall what else. It also mentioned a replacement, and then a rebuilt engine.
Whatever, it had a holed/broken piston when I bought it. I did speak to the so called expert who did the work on it, he was suitably vague and defensive.
Stripdown revealed:- No goodies, low spec engine, serious meltown and liner wear in one, some wear and water damage in another and two good liners and pistons. The gearbox looks good, crank is good, all rods have survived. I haven't stripped the oil pump yet, but did find 3 pins/rollers that look as if they could be drive pins loose in the sump - still trying to work out what these are if anyone can help - they are 20mm by 2.5mm approx.
I toyed with replacing the engine, but without finding one with history I was a bit loath. So, I have bought a used crank case, some good used pistons, and intend to do some mating. The liners are out of the case, honed and look good. The pistons and rings look like they will be happy in there. Next job is to heat the case and bang the two liners in. The issue I will have is I will need to top the block to bring everything back flush, and flycutting ally and cast together isn't my favourite job.
Pics? Yes, if I can, once things start coming together.
One question, if I may - if this engine is a replacement, low spec, (3uf) if I recall, do I need to do anything special - rods, cams, valves Any different?
Edit to say - I pulled the top off one carb - it had full power slides - no restrictors, the power valves are fitted, and there is a lot of evidence of modifying (plugged hole in the slide), ham fisted bodgery - hex head cover screws with at least one stripped thread, many of the phillips float bowl screws butchered, ditto the rack mountings, and the sync of the butterfies is visibly way out, as is the enrichment.
Tomorrow I will attempt to unscrew the head studs out of the scrap cover, knock in a pair of liners and jig it up for a flycutting test.

 

[user 16790]

wow, can't help with any info but good luck with it

 

[one2dmax]

Need to post up some pics. The liners should be in place before any honing (or boring) is done because they will have slight distortion occur when they are in place. You're likely going to be ok but that's not typical engine etiquette.

The rods/pistons, cams and misc are all more or less the same. You can post pics and I can review them to make sure.

You should not need to deck the block if the sleeves are full seated unless you are getting new sleeves. You can if you want but keep it to a bare minimum. When you alter the deck height you change the fitment of the intake and exhaust components.

 

[huw s]

Thanks, appreciate one of the named guru's taking the time to respond to a newbie. I must admit I am asking myself why I didn't just buy some new pistons and bore and hone the block. Never mind - too late now.
The replacement liners are 7 to 9 thou taller in the top hat measurement - meaning they will stand proud by that amount - I can't see it going any other way.
On the carbs issue - is the number marked on the needle? And how many and what size holes should be in the bottom of the slides?
Thanks,
Huw

 

[one2dmax]

The needles will be stamped with a 4 digit (sometimes 5) number and letter code. Post up pics.

 

[sdt354]

An unexpected side benefit of using the stage 7 needles, including increased top end and mid range power, was some very good mpg.

 

[huw s]

Thanks for that Sean. Looks like I have the No5 needle, so at the moment to the best of my knowledge I have full power carbs. I will get to checking jets later.

 

[one2dmax]

The stage one are junk and far too often people get sucked into believing that they are the best ones out there for mild or stock bikes with stock or slip-on mufflers.

 

[huw s]

Oops, my mistake, the ones I have are No4 in the list.

 

[huw s]

Engine rebuild on stop for a few days - wifes dragging me off to Cyprus and 2 days ago while making a jig to mount the top case in my miller the inverter drive died. Be 3 weeks till I know if it's fixable.
In the meantime I bought some used front pegs and mounts, including brake lever and pivot - the trike came with some reasonably nice forward controlls, but one thing I learnt riding my previous trike was that to drive quickly you needed to have your body weight inside the seat/bars centre line. Otherwise if the turn tightened you find yourself trying to pull the bars 'round whilst hanging on by whatever means. Anyway, to shift your weight you need your feet under you, hence changing back to original pegs - I will however, be keeping the forward sets as well, if I can.

 

[huw s]

It's been a while....
But hey, how about an update?
The fitting of a pair of good, used liners went OK. The flycutter in my miller did a good job of skimming the head to a perfect flat finish. That's when things went wron - on checking properly my earlier statement about the crankshaft being good was bollocks - it has 3 thou of wear in the main bearings. Is this normal?
Anyway, can't get undersize bearings other than the selective fit ones - does anyone here know what the range is on these from max to min? Maybe I could get someone to do a light grind? Cheapest ebay crank in the UK is £200
So, given summer is on its way, for now I bought a complete, low miles engine (so the ad said).
It's later than my original, so had to remove the flywheel. That's when I found a 6mm short bolt in the bottom of the casing, which is when I dropped the sump to find the return oil tube lying in the bottom, with the orange o ring split and hanging out. I fixed the o ring issue with a couple of blobs of solder to bias the main oilway tight against the casing, oh, I also ground a bit off the end - essentially the first 'rib' in the o ring tube so it goes in further.
Swapped the flywheels, refitted everything, did a bench carb synch and v boost disc synch. Engine now running, but I will need to strip and check the carbs properly - I know I need a new mixture screw, the head is gnarled up.
I started the job of fitting normal footpegs and controls, some fabrication needed.

 

[02GF74]

where has the radiator been relocated - best place is at the front to get air when moving; I have never seen a radiator cap so far down - usually sits near top of the cooling system

 

[huw s]

Poor pic - it's just hanging there by the bleed pipe, this was during the refit process - nearly a year since it came apart, sort of like a big angry jigsaw..
Any info about the crank grinding would be appreciated, I'd like to save it - thrusts and big ends are good.

 

[Fire-medic]

http://vmoa.net/VMX12-Service-Manual01.pdf

Check in here.

 

[huw s]

Thanks, some useful stuff in there not in my manual, but alas, no info on the size range of the bearings.

 

[Fire-medic]

Ask Sean Morley, he can probably tell you what the sizes available are, I think they're color-coded. [email protected]

 

[huw s]

Ask Sean Morley, he can probably tell you what the sizes available are, I think they're color-coded. [email protected]

Sean, can you help here - my logic tells me the range doesn't go down low enough?
3 thou wear means taking the journals to 6 thou undersize...

 

[one2dmax]

They total thickness difference between them all is not much over .001"
If you have wear on the crank then the crank has to be repaired (by welding and recutting) or replaced. BUT, the only time I have seen that much wear is when they have spun a bearing which makes the crankcase and crankshaft both junk

 

[huw s]

For some reason I had .8 thou between each onein my head?
I had been considering welding and hand finishing. What process and rods to use though? The casings are good, no issues with bearings or thrusts.
What you're saying about not seeing wear is a positive though - means it's less likey someone sells me a duff one.
Last edit, finish with a question - there is 8thou crank end float on the replacement engine I bought - please tell me this isn't terminal?

 

[huw s]

Pics of crank wear, mostly either end bearing, and in each case on the counterweight side - like it's overcompensated.
Centre bearings not too bad, big ends fine, thrusts fine