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.
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?
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.
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 :-)
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.
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.
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)
Thanks Philip. Interesting to see the various types of crankshaft - that 650 one has one heck of a big flywheel.
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
Goodbye Hannah - We'll never forget you !! Howard
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
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.