Dominator 88 oil pump driven gear

The gears are in matched pairs. The 6 start is not compatible with the 3 start gear. Some people did fit 6 start gears to their standard Dominators - there was nothing to be gained from it so reverting to 3 start makes sense. Just make sure your rocker oil feed is from the return to the tank (as it should be) and that you have scrolled rocker spindles.

Hopefully attached or nearby will be 2 pages from an old Roadholder which should answer a lot of your questions.

Despite the diagrams being a bit non-scale the difference between the angles of the worms is fairly obvious. The 6 start pair have a steeper angle to the worm.

To test that you have a matched pair....balance the gear on top of the worm so that they are meshing. They should be at right angles to each other, as they would be in use on the engine. If they do not make a clear right angle then there is possibly a mix of 3 and 6 start bits. Mixed components will make an angle around 80* ( or 100*).

The oil pump driven gear was generally marked with a 6 on its end but not always.

Attached is next page of Roadholder Oil Pump Article. Page 4 (not attached) has all the part numbers.

The NOC spares Scheme sells these kinds of parts.

Impossible to run with mismatched gears - they just wouldn't mesh.

Previously jon_osborne wrote:

I currently have a 6 start worm gear oil pump drive fitted which is incorrect for my 1956 Dominator. When I built this engine I used the parts I had which was the 6 start gear and a driven gear which fits on the end of the oil pump. This was 1998 and as I recall, I could find no reference marks on the driven gear to identify whether it matched with a 3 start, 6 start, or both, worm gear. I intend to go back to the 3 start gear as they are available but not sure if my driven gear will be ok. Can anyone advise how you can tell what worm the driven gear matchesand, if there are two types of driven gear, where I might obtain a 3 start worm compatible one?

many thanks

Jon

Hi john, I have a matching 3 start set-up,, interested in a swap? I am in N Lincs.

Previously Gordon Johnston wrote:

Impossible to run with mismatched gears - they just wouldn't mesh.

Gordon.......for the very first time evr (I think)I am going to have to slightly disagree with you. Having many years ago dismantled an engine which had a 6 start worm on the crank but a 3 start gear on the pump. Somebody had told the owner that his engine would have a better oil feed with a 6 start set-up. The guy had changed one of the set but did not realize he needed to change both. The engine was incredibly stiff to turn over, which was why I was called in, but had been running. On inspection both gears had chewed the life out of each other and were only fit for the scap bin.

Attached photo shows what the respective pairings should resemble when correct and when wrongly matched.

Previously jon_osborne wrote:

Hi Terry,

I was just going to buy the matching pair on NOC spares now I have seen the driven gear. Happy to give you what comes off (6 start pair) when I take the bike apart.

Let me know if you are interested - I am in Central Scotland

hello Ian give me a call on 07519710121 any day before 8.00pm, the gears that I have are in very good order, If you let me have your address, will send them to you and if you dont want them just post them back to me, or send your set. Terry

I too am in central Scotland and have 3 start gears if you want them. When you fit the oil pump, the pump gears engage with the gears on the crankshaft. If someone forced a 6 start onto a 3 start gear, it would require astonishing brutality. Ouch. Gordon.

Hi Jon, I'm near Biggar. I'll go and have a dig in my oil pump drawer to check condition but they will be in good order. I'll check if I have any 6 starts. If not I am sure I can find a home for them. My bike has a wiring glitch - no llights earlier this week - so I am attacking it with a multimeter to find the cause. Doesn't stop it starting first kick though - I do love magnetos. Gordon.

Previously terry_odlin wrote:

Previously jon_osborne wrote:

Hi Terry,

I was just going to buy the matching pair on NOC spares now I have seen the driven gear. Happy to give you what comes off (6 start pair) when I take the bike apart.

Let me know if you are interested - I am in Central Scotland

hellojon give me a call on 07519710121 any day before 8.00pm, the gears that I have are in very good order, If you let me have your address, will send them to you and if you dont want them just post them back to me, or send your set. Terry

Hello Jon, gears were posted today(wednesday) Terry

Previously jon_osborne wrote:

Previously jon_osborne wrote:

Previously terry_odlin wrote:

Previously terry_odlin wrote:

Previously jon_osborne wrote:

Hi Terry,

I was just going to buy the matching pair on NOC spares now I have seen the driven gear. Happy to give you what comes off (6 start pair) when I take the bike apart.

Let me know if you are interested - I am in Central Scotland

hellojon give me a call on 07519710121 any day before 8.00pm, the gears that I have are in very good order, If you let me have your address, will send them to you and if you dont want them just post them back to me, or send your set. Terry

Hello Jon, gears were posted today(wednesday) Terry

Hi Terry, Gears arrived yesterday (Sat.). Thanks, will be in touch when I have swapped them. Regards Jon

Latest update on this is that I have now taken my engine apart - slight rub on LH cylinder (fitted with JP pistons) but thats another story - and removed the oil pump and driving worm. The photos show the 'as fitted' 6 start worm and driven gear along with the matched 3 start pair from Terry Odlin. Clearly my driven gear as fitted is running around 5-10Deg from its expected natural centreline and has been in service like this for at least 4,000miles. The gears are shown deeply engaged and when fitted to the bike are less engaged allowing the gear to twist and sit on its centreline.

Terry, my driven gear is the same as yours and so I cannot send you a matched 6 start pair. Do you still want the pair; they were running ok after all?

Finally, by returning to a 3 start gear I will half the oil flow to the engine. Given it has partially seized on the LH side is halving the oil flow a good idea??

Hi Jon, just send my original parts back please!

Have a great new year!!

Terry

Previously jon_osborne wrote:

Previously terry_odlin wrote:

Previously jon_osborne wrote:

Previously jon_osborne wrote:

Previously terry_odlin wrote:

Previously terry_odlin wrote:

Previously jon_osborne wrote:

Hi Terry,

I was just going to buy the matching pair on NOC spares now I have seen the driven gear. Happy to give you what comes off (6 start pair) when I take the bike apart.

Let me know if you are interested - I am in Central Scotland

hellojon give me a call on 07519710121 any day before 8.00pm, the gears that I have are in very good order, If you let me have your address, will send them to you and if you dont want them just post them back to me, or send your set. Terry

Hello Jon, gears were posted today(wednesday) Terry

Hi Terry, Gears arrived yesterday (Sat.). Thanks, will be in touch when I have swapped them. Regards Jon

Latest update on this is that I have now taken my engine apart - slight rub on LH cylinder (fitted with JP pistons) but thats another story - and removed the oil pump and driving worm. The photos show the 'as fitted' 6 start worm and driven gear along with the matched 3 start pair from Terry Odlin. Clearly my driven gear as fitted is running around 5-10Deg from its expected natural centreline and has been in service like this for at least 4,000miles. The gears are shown deeply engaged and when fitted to the bike are less engaged allowing the gear to twist and sit on its centreline.

Terry, my driven gear is the same as yours and so I cannot send you a matched 6 start pair. Do you still want the pair; they were running ok after all?

Finally, by returning to a 3 start gear I will half the oil flow to the engine. Given it has partially seized on the LH side is halving the oil flow a good idea??

Hi Jon, just send my original parts back please!

Have a great new year!!

Terry

Gears posted today Tues 31st. Will buy a 3 Start from the NOC

Happy new year to all

Best-regards

Jon

Hi Jon, gears arrived safely today, thank you - Terry