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Help needed with D1 lack of power
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Martin Parry
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October 11, 2021 - 9:24 am
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Hi everyone - I posted the article below around 2 years ago and although I received lots of good advice, nothing was successful.  It's still stuck in my garage and in need of a new burst of enthusiasm and know how.  I'm still keen to get it on the road and take it to club events - does anyone know any people close to Lincoln who might help?  I'm happy to deliver the bike and leave it with them.  I'm not sure if Rusty Rooster is able to help but it's a long way if I can get someone local.

I've recently restored a 1952 plunger D1 and have a power loss issue I can't cure.  The bike was my Dad's and I wanted to get it back on the road, rather than sitting in a garage.  The problem is that it won't pull in third gear.  I've checked the sprockets and the ratio is correct; I've changed the carburetor with a good runner; I've sent the Wipac assembly off and had it renovated; I've had a new silencer made; it has a new plug; I've renewed the fuel line and filter; the rengine was rebuilt by an old chap who used to work on the bikes (so I hope he did a good job); it's been rebored and new rings (according to the BSA mechanic) - none of which have cured the problem.

I am desperate to get the thin running so I can join the club and take part in events but am at the end of my expertise - I thought I was pretty good with 2-strokes having had (and tuned) a Yamaha FS1E in my youth, but I'm beaten.  Can anyone help?  I live just outside Lincoln.

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GlenAnderson
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October 11, 2021 - 9:52 am
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I chased a problem with my D1 for years and it turned out to be the wrong flywheel. Magnets in the wrong place relative to the keyway meaning a poor spark. 

Whatever the issue is, it will be something simple. 

Remember, though, a D1 is hardly a ball of fire, even when running perfectly. 

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Martin Parry
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October 11, 2021 - 9:58 am
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Thanks Glen - the flywheel is part of the original engine, so I doubt it's my issue but good to know anyway.  It might not be a ball of fire, but a slow steady smoulder would be something!!!

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stubaker58
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October 11, 2021 - 10:54 am
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Hi,

even a correct crank assembly can go wrong! A sudden stop (seizure?) can twist the shafts in the flywheels (the piston has stopped but the flywheels continue to turn) and put it all out of kilter.  In effect what happens is the timing is put out as the groove for the woodruff key ends up in the wrong relationship to the con-rod. They can be checked and sorted or it can be over come with an electronic ignition which no longer depends on the cam.

regards.

Just realised the above post was about the generator flywheel (rotor) not the crank flywheel! Doh! Glen is right though, the magnetic flywheel does come in different guises and could have been changed in the life of the bike.  

The stuff about the crank still applies and is worth checking, it’s possible to leave out the tiny woodruff key so the cam rotates on its shaft, time the engine up and then tighten the cam screw.  The taper should hold the cam for a test ride.  If it’s better problem solved or at least identified!

“There’s nothing new under the sun”.

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cocorico
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October 11, 2021 - 11:47 am
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stubaker58 said
... Doh! ...

I think you are still a little confused, Stu. whistle On a D1, the generator flywheel is keyed on a taper, the cam is keyed on a parallel shaft. If the crankshaft has moved in the crank flywheel, the timing can be affected. In that case, both the gen flywheel AND the cam could be moved by removing their woodruff keys. The gen flywheel will hold on the taper when the nut is secured and the tightness of the cam screw and lock washer SHOULD be enough to hold the cam. A good example of this is on a topic by Dimitris from some years back - make a cuppa and settle down for a long read. ** Please log in to view **

Of course - we could be barking up the wrong tree - remember..."if you think it's a fuel problem, it's ignition. If you think it's ignition, it's fuel". What fun!

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Martin Parry
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October 11, 2021 - 12:38 pm
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The option of an electronic ignition is top of my options but I'm looking for another pair of eyes before adding to my £1400 spend thus far and still not a roadworthy runner.  Thanks for the above replies though.

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cocorico
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October 11, 2021 - 1:05 pm
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I think you need it running on the Wipac system before spending on electronic ignition, which if you read some of the many posts on it, is not a cure-all. Power is very limited on a D1, even compared to a Fizzy, especially in modern traffic.

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stubaker58
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October 11, 2021 - 1:16 pm
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🤭 Thanks Coco, you are (of course) correct, and yes Dimitris’ saga is well worth the read.  Good point about not immediately going down the electronic route.

I’d try the points cam first. One thing at a time.

“There’s nothing new under the sun”.

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Sponge
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October 11, 2021 - 1:30 pm
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On a slightly different tack but a wuestion that needs to be asked......have you got a head gasket fitted to the D1 ?

Reason I ask is because I had a somilar problem with a beautiful smooth running D1 many years ago. Ran like a swiss watch but had no power. I had rebuilt the engine myself and because there was a head gasket in the set...I fitted it. Result .....even less power. 

Speaking to an old BSA works mechanic who said that D1s are not supposedto have a head gasket.....I removed the gasket...surfaced the head on my plate class block and re-fitted it with some HMP grease. 

Behold the difference....power restored and accelerates on the flat to 35/40 MPH. 

Worth a look ?

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Martin Parry
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October 11, 2021 - 4:03 pm
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Thanks Sponge - it does have a head gasket and I'll certainly give that a try when I next spend time with the bike - working away at present.

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rusty1
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October 11, 2021 - 6:11 pm
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These old engines need running in properly to give full power ........ several hundred miles ... many heat cycles... with mineral oil, to mate the piston ,rings ,bore together to get maximum compression, presuming you have noted all the other comment's and they are within tolerance.

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Number6
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October 11, 2021 - 6:36 pm
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Just in case - quote from topic "Head Gasket", June 29, 2015

"If you have the "Pineapple" shaped barrel then as far as I am aware there is no head gasket, the later "round" shaped barrels there is a head gasket."

Mike H --

Murphy's 4th law of motion states that any small object that is accidentally dropped will immediately hide itself under a larger object.

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Stoo63
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October 11, 2021 - 9:58 pm
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Definitely no head gasket. Check for air leaks and don't whatever you do squander more money on electronic ignition. 

Does it do 30?

'49 LE; '50 D1 Lucas; '55 D3 Battery; '58 Square Four (project); '59 D1 direct lighting; '60 5TA; '62 BSA Sunbeam; '72 Mobylette; '76 FS1-E; 

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lbayorkie
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October 12, 2021 - 8:25 am
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As has been mentioned D1s don't have a lot of power. My experience on flat roads is that you need to get up to at least 25mph in 2nd, then change up into 3rd and wait...and wait and wait for the speed to creep up to maybe 40mph. There's no pulling power in 3rd so maybe you are just expecting too much from the bike. 

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lbayorkie
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October 12, 2021 - 8:29 am
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It's also worth mentioning that the FSE1E has around 20% more horsepower and superior gearing so will have much better performance than a D1.

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Sponge
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October 12, 2021 - 9:05 am
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Hi Martin, some extra thoughts on this. Yes the D1 suffers from being low on power so it is important that you make sure it is running right and properly adjusted in all respects before measuring its performance.

You say that you had an exhaust made up ? Possible source of a blockage which might slow you down. Small 2 strokers are very sensitive to exhaust systems. So if all else fails it might be worth swapping it with a genuine BSA item to see what happens.

I have a D1 which runs quite well on a std engine, carb and exhaust, but I am very obese so all that extra weight  slows the poor thing down with a headwind or slight uphill. Nevertheless I can screw it up to 40MPH in favourable conditions which is fast enough for me. 

Suggestion. Invite some D1 owners over for a ride out and a performance trial. We can then compare performance and possibly do some swaps to see if you are getting the best out of your D1.  

So long as the date fits in my diary I would be happy to come over, or meet up,  on my D1 so that we can have a performance trial. Perhaps others might be up for that as well. Worth thinking about ?? Suggest speak to your area rep to see if he/she can help.

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toppo46
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October 12, 2021 - 8:30 pm
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Evening Martin,the Lincolnshire section are meeting up at the old station at Barney on Saturday morning.It might be worth popping along . Regards John

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rusty1
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October 13, 2021 - 5:14 pm
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You could try and find one of these........ it gives an extra 20%

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rusty1
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October 13, 2021 - 5:15 pm
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toddy-1.jpg

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cocorico
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October 13, 2021 - 6:18 pm
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rusty1 said
You could try and find one of these........ it gives an extra 20%  

... after you've sorted the problem. Not a lot of power plus 20% of not a lot is still not much.

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