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Dommie 88 frame/engine clearance

Submitted by jon_osborne on Mon, 10/02/2014
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Heavy Twins

I noticed when I removed my engine that the RHS crankcase at 6 o'clock has been rubbing the RH frame tube. Can anyone advise if all wideline frames were identical (including the Model 50 and Model 7) and whether all engine plates are the same? Could I have 99 plates with an 88 engine or some other combination? Engine is definitely an 88 from the engine number but not sure about anything else as it came as pieces.

thanks

Jonathan

Submitted by phil_hannam on Mon, 10/02/2014

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Many owners find that the engine cases rub on the plate corners. But not generally on the frame. The clearance between engine and bottom rails is a bit tight in places but usually there is at least a 5mm gap. The exception is the 1/4 engine plate stud behind the sump. This sits right between the rails with very little room either side. It is a real pain as you have to raise the engine above the bottom rails to remove it unless the plates have been slotted.

88 and 99 engine plates were identical as the same crankcases and gearboxes were used for both motors. It is possible that you have some home-made engine plates or a frame with a kink in it.

Can you take some photos and upload them?

Submitted by phil_hannam on Tue, 11/02/2014

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Model 7 crankcases were almost identical to early Model 88 and 99 Dynamo cases. The engine mounting plates were different because the Model 7 had a single downtube at the front of the frame.

The later Alternator cases had a different timing cover and a different arrangement for the primary cases but all of the engines would fit in a Feathebed Frame.

There are a few possible causes of the rub marks. The most obvious being that the engine plates were not positioned correctly on the frame lugs and have pulled the engine over to one side. Unless someone has repositioned the lugs.....the front engine and rear gearbox plates should both sit on the outside of the lugs.

It may be possible that your frame was previously used with another engine, eg Triumph and the front mountings changed or lowered.

What are the lug mounting holes like sizewise? They should be identical in bore to the engine cases and all take 3/8 bolts and studs plus one 5/16 stud in a very close fit.

One last thought........on my Dommie, the Speedo cable runs alongside the engine by the bottom right frame rail and often grinds away the paint.

Submitted by jon_osborne on Tue, 11/02/2014

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Thanks for the info Phil. It appears my engine plates have been fitted correctly on the outside of the lugs. The lugs themselves look as though they are as original, i.e., no signs of any other past welds present.

The front holes seem concentric and have very roughly about 1 mm diametral clearance on a 3/8" bolt.All holes in the engine plates are round and have about thesame clearance.

I may be able to get around 5mm clearance by using up all the clearance in all the holes but not sure if if it will stay there or vibrate down to bottom of each holes (which I think is what has happened as my engine bolts were loose)

Note my speedo cable (seen in photo) also runs along this tube but is on the outside of the tube and not trapped between the engine and tube

 


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