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Seized engine
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stu
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August 10, 2019 - 7:04 pm
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Any suggestions on how to unfreeze a D7 engine that has not run since 1972 approx, it was stored with the plug in but is solid.

After drowning it in diesel for a week, I have removed the cylinder head and was amazed that the piston head was as shiny as a mirror, and stuck at TDC.

Any ideas??????????

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chickensoup
Bolton, Greater Manchester
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August 10, 2019 - 11:47 pm
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Hi Stu,

Glad to hear your engine has been soaking. I take you have removed the clutch basket and kick start assembly,  along with the stator plate and fly wheel.

I would imagine that your engine has seized in 2 area's. Firstly the bore, where the bore and piston rings have become rusty and joined as one. Secondly the crank, where the bearings have also become rusty and wont turn.

That barrel needs to come off first if possible. A tin of WD40 and a heat source is required. I use an electric hot air gun ( one used for paint stripping ) a blow torch could also be used. Get that barrel up to about 200C when the WD40 starts to smoke and see if you get any movement. I  also wear a pair of riggers gloves here, so as not to burn my hands. 

With the cylinder head off you may also be able to remove the 4 cylinder head studs. This will enable you to crack the base gasket easier and in turn may allow more movement of the barrel to free up those rings.

Be patient, a combination of heating, cooling and re dousing with WD40 may free it all up.

If all this fails, you will have to split the crank cases with the component still seized, remember to remove the 2 locating dowls ( thin metal tubes ) these are pressed into the top, front and back engine mountings, where the engine is bolted to the frame. These are also a pig to remove, use plenty of heat and WD40. I drift them out using a round bar slightly smaller than the diameter of the hole in the crank cases Plenty of support is required underneath the engine mount area, as I have found that quite abit of force is required to remove the dowls, using a hammer and your drift.

with the dowls removed, along with all the retaining screws and cylinder head studs the 2 crank case halves should separate.

You should by now have your 2 crank cases and gear box components all separated from your seized up components ( the crank shaft, piston and barrel )

You should also now be able to free the piston from the bore a little more easier, as you should be able to get to more of the bore.

hope this helps you or at least puts you on the path.... Nick

1950 BSA D1 Plunger   242 UYW

1966 BSA D7  LBF 62 D

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johnsullivan
east sussex
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August 12, 2019 - 10:05 am
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ACF 50 will outperform WD here.I revived a JAP mower engine the other week.U/D.but it is a remarkable product..? If you can see the rings through the exhaust port then apply fluid you can tap the piston  rings  with a bit o f wood .The hot airgun up the port may well help too. the piston is at the top try to keep the heat to the edge .Have you removed the crankcase drain plug? If you invert the engine it is possible to put the freeing agent under the piston this can help free cranks too,simply fill with diesel .One big advantage of strokers.

67 D10. and a D7    2007 Honda Hornet FA. Honda CD200 81 93 Yamaha TTR 250 Raid, Sinnis SC 125.   75 Montesa Cota 247 an electric scooter of Famous make.

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cocorico
Central France
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August 12, 2019 - 12:13 pm
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Just to point out that, although it's very useful for all sorts of things, WD40 is not actually advertised as a penetrating fluid. There have been conversations on the forum before on what makes the best freeing agent! popcorn

Personally, for smaller jobs I tend to use a proprietary release agent; for bigger jobs I use diesel fuel or a mixture of acetone and thin oil (usually hydraulic oil).

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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cocorico
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August 15, 2019 - 11:05 am
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cocorico said
...Personally, for smaller jobs I tend to use a proprietary release agent; for bigger jobs I use diesel fuel or a mixture of acetone and thin oil (usually hydraulic oil).  

I see that 'Plus Gas' is still available (at least 'over there'). I remember first using it in the 50s / 60s (old) and I don't think it's been beaten as a freeing agent - must get some brought over for me. Might be worth a try on your seized piston / rings, before you resort to gentle persuasion with a mallet...

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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johnsullivan
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August 15, 2019 - 12:04 pm
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plus gas has been reformulated from its intoxicating original formula.** Please log in to view **

67 D10. and a D7    2007 Honda Hornet FA. Honda CD200 81 93 Yamaha TTR 250 Raid, Sinnis SC 125.   75 Montesa Cota 247 an electric scooter of Famous make.

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cocorico
Central France
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August 15, 2019 - 8:32 pm
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johnsullivan said
plus gas has been reformulated from its intoxicating original formula....

Spoilsports!

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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johnsullivan
east sussex
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August 16, 2019 - 8:04 am
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Handy way of saving money these safety sheets.

67 D10. and a D7    2007 Honda Hornet FA. Honda CD200 81 93 Yamaha TTR 250 Raid, Sinnis SC 125.   75 Montesa Cota 247 an electric scooter of Famous make.

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stu
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September 8, 2019 - 9:49 am
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Thanks for all your advice fellow Banty's, we have success.

The piston and barrel parted company with very little effort, but the splitting of the crankcase was another story.

Having removed some of the gumff on the case I discovered a nasty longitudinal crack which did not fill me with great joy, but looked salvageable with an aluminium filler rod and heat. The dowels had to be drilled out as no amount of persuasion would budge them, I drilled the out with a slightly smaller drill and then collapsed the remains with a pin punch.

Next came the job of drilling out all the badly damaged cross head bolts after investing in a impact driver and discovering that I couldn't budge a single one, even after applying heat and several explicit's.

Meanwhile I discovered on eBay a crankcase assembly which I bid on and won HOORAY!!

Eventually after many attempts I have successfully separated the cases and removed the crank, which is seized solid, and the plates part number 70-7796 extremely corroded which I am now in the process of removing.

My question to you all how to remove the lower crank pin, do I need the facility of a fly press or is there another method known ???

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sunny
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September 8, 2019 - 1:32 pm
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you  will  need  a  set of  tools  to  dismantal     &  asemble  the  crank  a hydrolic  press   most   send  them   away

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SpacedMarine
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September 8, 2019 - 3:59 pm
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As sunny says getting them apart is pretty easy with a press.Putting them back together is a bit harder as you have to get them to run true to within a couple of thousands.Possible on a lathe or a stand between centres.Easiest to get someone to do it unless you have the equipment. 

What's 7/16 in mm again?

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stu
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September 8, 2019 - 7:23 pm
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Any suggestions for a company to carry out the big end replacement, and another one for the plates ???

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Mick W
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September 8, 2019 - 8:34 pm
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This Guy is a two stroke specialist and will do what you are after. ** Please log in to view **    I have used him for a rebore and he was excellent. I know nickjaxe has used him for a big end replacement.

This recommendation is a personal opinion

Mick

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cocorico
Central France
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September 8, 2019 - 9:02 pm
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Alpha Bearings in Dudley have a good reputation for crankshafts. As for the flywheel plates - many of us have removed them when they have come loose, with no noticeable change in performance - just try Googling "flywheel plates site:bsabantamclub.com/forum" to see!

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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SpacedMarine
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September 8, 2019 - 11:28 pm
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cocorico said
Alpha Bearings in Dudley have a good reputation for crankshafts. As for the flywheel plates - many of us have removed them when they have come loose, with no noticeable change in performance - just try Googling "flywheel plates site:bsabantamclub.com/forum" to see!  

The latest iteration of my crank currently has no plates and its relatively speaking (I know you'll laugh when I say this coco) "faster" than it's ever been although it is slightly lighter and balanced for a rex caunt rod and piston.

What's 7/16 in mm again?

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