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Micks D3 Repair/Rebuild.
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MOSOGER
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September 8, 2016 - 12:41 pm
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Following a thread on D3 parts, I have decided to document a D3 Engine project.

For comments and advice on all things D3.

At present the head and Barrel has been removed and below are some photo's of first problem's and queries. 

The casings are matching Numbers and have very few marks, with original fixings in very good condition, although someone has been inside at some point in its life as the tell tale signs of the screw driver are present, but not excessive.

The first photo is of a serviceable D3 head, this is a for a comparison to the one we took off,

 

 d3-head-0061_zpsvfcqyq3q.jpgNote the shoulder thickness, aprox 1/8 inch 125 thou.

Next photo is of the one fitted

004_zpsdvoqrhow.jpg

Virtually none existent, shame really as there is no damage to the fins at all.

It hasn't been machined off it looks like a 9 inch hand grinder by the marks, I think this has caused the next problem in the next photo.

 005_zpsrtuivfzb.jpg

Note the gap at 7 o'clock.. there isn't any, its actually catching on rotation.... Boomerang comes to mind...

Also the piston was missing .? its probably in the sump.

Next photo shows the barrel NOT sure if this has been ground back as well looks a bit thin on top, and is uneven.. Comment please, also shame as it is 57mm which is apparently standard.

003_zps2eh1a2un.jpg

A couple of questions please .... is the crank beyond repair.?  is that barrel correct or unserviceable.?

Lastly to open up the possibilities of spares, what other models use the same dimensions ie I believe some D1 parts are identical.

Not split the casings yet estimating that the con rod is bent, judging by the crank, although I could not detect any play in the big end, and the end float feels spot on.

Comments please.. also any serviceable parts lying around for sale would also be appreciated, or maybe a source for the above bits would be of great assistance.

Further updates when casings are split.

Bob.

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Anderzander
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September 8, 2016 - 9:41 pm
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Hello Bob

Both of those surfaces look possibly standard to me? It's hard to tell on the head though as that does look flat and scored. I put a post in Ferguson's go faster thread recently commenting how wide the variance is on a number of standard heads I have. On one D1 head the machined face is almost flush to the underside of the fin (not looking that dissimilar to yours) - on another is it 5 mm higher.

One of my cylinders is similar - and even with not to nothing there I've managed to have that skimmed. So your cylinder definitely looks workable to me.

Stephen

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ferguson
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September 9, 2016 - 12:09 am
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one point that i've found to be pretty consistent with bantam heads is that whatever they look like the depth of the crown is pretty much the same on all like for like heads.so measure crown depth to see what has been taken off or not[i'd guess its been skimmed a bit too far].the barrel looks perfectly normal-they all tend to have a lower shoulder than the heads.

dont presume the worst for the crank-if the head been over skimmed and been a wee bit of contact the crankshaft/or its been seized sometime then most likely just been knocked out of alignment rather than the rod bent.rods are pretty tough but the crank pin easily knocked out of true.just dropping the crank on the bench is enough to put it out.when you get it out measure outside diam across the pin and then compare it to opposite side[180 degrees].should be same give or take 1 thou but if had a clunk then non pin side often closes up[or opens] which causes a wobbly crank.tap in a hard wood wedge[or a couple of tyre levers] until both halves of crank parallel.if opened up close it with a g clamp-then its plonk it on a couple of v blocks and check run out with dial gauge where the bearing faces are.judicious taps with a brass hammer/rubber hammer will soon get everything about true.bantam's will run quite happily with 5 thou 'wobble' on the bearing faces but if you get it down to 1 thou float each end it will purr in comparison. if you are lucky takes an hour if unlucky can take hours to true but well worth it.

for the barrel i would just lap it down to flat on a piece of flat glass with some grinding paste.

ferguson

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September 9, 2016 - 1:11 am
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Thank you gentlemen for the input. tip-my-hatthumbs-up

So there's hope for the Crank and barrel, I was reading another thread posted by nickjax on a firm who specialise in two strokes up north.

May get them checked out before any expense. (thanks nickjax).

Fergerson don't think it has been seized but there is a strong possibility the piston struck the head, as the piston is missing, meanwhile I can measure the distance to the Crown of the head from a straight edge, I don't suppose you have the correct distance it should be as standard.

Once again on the behalf of Mick who is the owner and myself for the info. THANKS... perhaps one day another D3 may run under its own steam again.

Will post results for future reference and interest.

Bob.

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ferguson
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September 9, 2016 - 10:26 am
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afraid i dont know measurement of depth of crown for a d3.d1's are near enough 3/4 inch[19 to 20mm covers most standard d1 heads].you will need to find a standard head or ask someone with one to measure theirs for you.

ferguson

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Anderzander
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September 9, 2016 - 10:52 am
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I have a standard D3 head Bob - do you want me to measure the depth of the combustion chamber from the mating surface?

My experience is the same as Ferguson's - When I compared my 2 D1 heads - where one had a large shoulder between the mating surface and the fin - and the other, next to none - I checked the combustion chamber depths by placing a straight edge across the centre and then measuring the depth with a vernier gauge and they were both the same.

I think that what was happening is that the castings were made to a significantly broad tolerance - and then machined to as close to the right dimensions as possible, giving us this variance in deck heights etc.

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September 9, 2016 - 12:14 pm
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Cheers Stephen would appreciate that very much.

Regards Bob.

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September 14, 2016 - 10:32 am
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Couple more interesting photo's.

Comments please.

m2%20007_zpszvslmrca.jpg

Clutch plates with a few corks missing, the strange thing is there's no trace of any bits, it's as if it was assembled this way.? surely it couldn't have devoured them completely.

m2%20003_zpsfz67opnc.jpg

Rear of fly wheel it appears to have had a bolt jammed behind it at some time, again NO sign of what ever it was, also the fixings were all in place on the carrier, nothing unaccountable or missing.

As you are aware there is a natural hole at the bottom about an inch square but what are the odds of a bolt flicking up there and then falling out again.

Now contemplating fabricating a mesh guard for mine to stop any pebbles entering.

m2%20006_zpsxlgpjwkk.jpg

This shows where it was wedged up against, although it looks bad I believe the casings will except a new seal and could be re-used.

I now think this is the culprit that bent the crank, not the cylinder head.

Quite bizarre findings.. and comments gladly taken.

Regards Bob.

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Mags 1
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September 14, 2016 - 12:31 pm
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Looks like someone was in a hurry or couldn't afford the price of a flywheel puller and used the bolt as as wedge?

Sorry Bob, but 'except' instead of 'accept is' one of my pet peeves! Sorry, nothing personal!get-me-coat

Four now on the road and at least several in bits.

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September 14, 2016 - 4:17 pm
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Mags 1 said
Looks like someone was in a hurry or couldn't afford the price of a flywheel puller and used the bolt as as wedge?

Sorry Bob, but 'except' instead of 'accept is' one of my pet peeves! Sorry, nothing personal!get-me-coat  

No problem Mags 1 ... thanks for pointing it out, it's the way I was dragged up, there was eight children in our family.

I was lucky to eat let alone learn English properly, as for school I couldn't go until I was 9, that's when I got my first pair of shoes.

I say shoes they were me Dad's old wellies.

My father was very strict he leathered me every time I mocked the afflicted, so I live and let live now.

Sorry to hear you have more than one peeve as you talk in the pleural. (peeves).

PS interesting theory to the damage on the fly wheel.

Regards Bob 

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ferguson
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September 14, 2016 - 5:52 pm
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have to agree with mags 1 -that's typical damage done to remove the flywheel without the use of a puller.the 'natural hole' is missing on some bikes and it used to be common to see where owners had bashed it open to get at back of flywheel so they could remove the flywheel.[back in the 70's flywheel pullers were like hen's teeth-just unobtanium-as were clutch compressors] so people 'improvized'.dont forget back in the '70's the bikes were worth nothing so nobody bothered to buy special tools for them-just got round the problem.

ferguson

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September 14, 2016 - 6:07 pm
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It does look like it would take a new seal though - and I'm sure you could clean it up a little and mark the rest down to history / character.

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stubaker58
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September 15, 2016 - 10:17 am
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I have been known to use (car) tyre levers on mine (FAR 92G where are you?) needs must when you're (were) a student!  It is easier with the proper puller though.

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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