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What’s my crankshaft from?

Forums

Hi.

My Domi 99 is becoming more like a ‘Who done it?’ mystery every day.

I did a bit of research in the Club archives and found a really informative article called ‘Dominator mix and match’. The description of the various crankshafts has got me puzzled/worried as I’m now wondering if my crankshaft is from a 650 rather than a 600 (please see attached photo). The reason for thinking that it might be from a 650 is because the article I read said that 650 cranks have “full circle flywheels with cut-outs in the rim to allow for piston clearance”. Mine looks ominously like that! However, the big end journals are 1.478 inches diameter , which looks like it’s a -20 grind on a 600 crank - very confusing.

If it is a 650 crank, should I be concerned - will it work ok in my 600 engine? Will the motor be sluggish due to the extra flywheel weight?

 I’ve already bought new shells for a 600 crank - would they now be unsuitable if the crank is for a 650? I’ve a hunch that the conrod journals  are different sizes for 600 and 650 crankshafts.

Thanks

Regards

Tony

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If you measure the big ends that will indicate what you have.  A 650 crank will not normally fit in std 99 cases. However if it is a 650 crank I would consider using it as spares and reliability would be better than old 99 stuff.

Thanks Robert. The big end journals are 1.478 inches in diameter. I believe that the standard 600 journals are 1.5 inches, so it looks like my crank is on a -20 grind. I’m just confused that the flywheel seems to be a 650 one. I wonder if it’s possible to bolt a 650 flywheel in between a pair of 600 big ends?

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As the throw of the cranks are different if it was possible to fit the wrong flywheel I think it would wobble back and forth as it revolved.  I have thought about fitting a 650 crank to my 99 ,it would involve making room for the big ends to clear the cases  and checking the clearance of rods to cylinders etc but would allow  better rods to be used, OIl system would need uprating and 650 pistons .(which are already fitted in my 99).I suspect however that when the big ends of the 99 give out ,a set of Thunder rods will be needed.The 99 is my "go to" bike and is running too well to disturb, I also have  three  other bikes in the familly needing heavy work.

Thanks David. My crankshaft definitely isn’t like the ones in your photo so I guess it’s the correct 600 one. That’s reassuring. Thanks again.

Regards

Tony

Hi Robert,

Upgrading from a 600 to make it have a 650 bottom end sounds like a lot of work and expense, with no guarantee of success. I’ve got enough problems just putting this engine together as a standard 600 :-)

Regards

Tony

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Its pretty well guaranteed that the 60 year old conrods will fail sometime. Sooner than later if the performance of the motor is used to the full or if  the rod big end eyes go out of round and someone fits new shells and does not check there is enough clearance.There is a finite fatigue life to these and who knows whats happened in the life of a bike. The 650 uses current rods so while there is a supply the motor can be rebuilt fully. The thunder rods are a practical solution ,I will look into these.

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If you dismantle the crank, you will find that there is a dowel in the centre of the flywheel, and a matching drilling in each of the crank halves.  You can measure the distance between the centre of the dowel and the centre-line of the big-end journal.  If that measurement is 41mm, you definitely have 600 cranks.  If it's 44.5mm, you have 650 cranks.  Or 750...  The dowel and crank bolts are the same.

Paul

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See attachments for a few more Dominator crankshafts to compare.

Tony's crank looks like it is from a 99 engine. The 88 crankshaft has a full centre web. Whereas the 99 and 650 both have sections machined off one side to give clearance  for the piston skirts. The 650 crankshaft as shown in both my photos and Dave's show similar machined sections but the centre web is considerably wider than those from and 88 or 99. (or Model 7 or 77)

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hello yes the 650 dose have a bigger fly wheel  but its a very balanced  fly wheel  the fly wheel job is to keep the motor turning over at speed and helps with the power out put,  as mass at speed gives off power but you have to get the balance just right,  its same with any motor  even a four cylinder,  as  for connecting rods  they keep doing there job no matter how old they are just have them checked out for any cracking  under a electromagnetic   spectrometer, even steam locomotives have this job done,  then get the reciprocating  mass all in balance  and next it to clean out all oil ways and get the oil pump checked out   and the cylinder head  checked out  for its oil ways and valves and seats and new Bronze valve guides  and you need to recut the valve seats to match the new valve guides  and make sure the  valve spring   insulating washers  are not covering the oil way holes  next to the valve springs  and its critical to get a good gas seal with the valves in the cylinder head  and rebuilding any motor  the preparation and cleanliness is  paramount  and next doing all the timing before fitting the motor back in its frame,   then check for alinement  of the engine between the clutch  and the rear wheel sprocket   you may find the rear wheel spaces are ether too big or too small  and the chain out of alinement  so check it  do not expect it too be in line  do not for get how many owners these bike has had  in it life span,   this may be the last information i will be putting on this web site  as members  just are  dismissing    my in put, so I feel I am just wasting my time,  with this Club  and I may not  renew my Membership  as I have No need of this Club the Communication between members is at all time low,  and restrictions on this web site is not helping  matters     yours  anna j  

hello howard  and thanks  but if you read I put I may not  renew my membership  I not come to a definite decision as yet, we see as this month progress,   just looking at buying a New royal enfield 650  twin  but need the Royal enfield to change over the brake and gear change to the old British side  right hand gear change and left hand brake  so I can ride it better  But then again we will see  my change my mind yet again  that us females prerogative changing our mind set  . my knees are not the best  and  there pain full  from time to time  well I am now pass 65,  and still riding when i can  , but not of late,  as i have other heath problems  water works being one and depression another and being on my own isolated has not helped  loss of interest    in motorcycles  over all  within the last six months or so,  so I am in need of some of you members to get me fired up again    and get back into motorcycling    , yours  anna j  

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Anna , some people may not agree with everything you post and that happens to everyone , me included but I think the mag would be a duller place without your input . It may take a while to get your mojo back but I'm sure it will happen sooner rather than later so come on gal , that cup is half full not half empty.

Pete

 

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