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Post by jon on Feb 13, 2022 10:33:23 GMT 1
No, not Allen Millyard’s ability with a hacksaw. Primary and secondary drives for a YPVS.
I’m considering this as a route to go with my latest YPVS. It’s a Mick Abbey tuned 385 with 17” rear wheel.
I know for the expense I’m not going to see that much gain with the standard ratio, but the +7% sounds interesting. Due to my setup I would hope this would not overhear it?
Second question is the maker. I seem to remember in the past gears being sold without proper hardening and wearing out pronto. Has anyone had experience of say Norbo’s or Mad Bikers?
Jon
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Post by headcoats on Feb 13, 2022 10:46:30 GMT 1
Yes mine were from Wicked and made of cheese and the geezer didn't give a f##k !
I wouldn't bother |
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Post by jon on Feb 13, 2022 10:51:57 GMT 1
Yes mine were from Wicked and made of cheese and the geezer didn't give a f##k !
I wouldn't bother Why wouldn’t you bother? Are you commenting on the short time they lasted they were no good? Or, obviously wouldn’t bother with Wicked’s ones? Jon |
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Post by headcoats on Feb 13, 2022 10:58:55 GMT 1
Well unless you are making mega horsepower I guess
I had some as a nostalgia trip as I had some TZ primary gears on my Harry Barlow tuned LC back in the day
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Post by Norbo on Feb 13, 2022 11:15:37 GMT 1
Yes mine were from Wicked and made of cheese and the geezer didn't give a f##k ! I wouldn't bother I herd that before about the US made ones . |
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Post by muttsnuts on Feb 13, 2022 11:16:40 GMT 1
not had to fit any to all of the 385's I've built, the stock gears are good for 80+bhp no problem, especially the way a 385 makes power, bit different if your running an Athena or cheetah cub kicking out 90+bhp as its not just the bhp, its more about the torque and the way the engine makes it, it comes in with a pretty hefty kick which hammers the helical gears and puts a lot of strain on the clutch side crank bearing, the straight cut gears help alot in this area.
You can get the extra 7% by just changing your front or rear sprocket ratios
HTH
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Post by Tobyjugs on Feb 13, 2022 11:23:21 GMT 1
Jon i have used the following,
Nova Gears: Super finished with a tooth clearance of 0.20mm. Good quality as expected but customer service can be excellent or crap as experrianced by me and others. Plug and play.
Norbo's Gears: I'm not sure if they are superfinished or just well made from the off. Tooth clearance is a bit sloppy at 0.24mm. This set is the most abused set of primaries i use. Currently fitted to a big bore engine with no signs of deteriation. Cheaper than Nova Gears and fantastic customer service. Pay attention to the clearance of the water pump thrust washer and the crank primary.
Liberty Gears (USA): Not used them much, not so keen on chunky crank primary gear. Off the top of my head i think the crank gear is higher than a standard crank gear.
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Post by stusco on Feb 13, 2022 11:31:26 GMT 1
Saw these on performance fabrication i dont know anything about straight cut but here’s the ad  |
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Post by midlifecrisisrd on Feb 13, 2022 12:04:07 GMT 1
I never bothered on mine, just used the standard helical gears
Know what you mean about gearing, I've got 17/41 with 17 inch wheel and it's under geared
I have a 39 to go on the rear which I haven't tried but I may just buy an 18t offset front sprocket
Steve
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Post by derek500 on Feb 13, 2022 13:13:06 GMT 1
Interesting stuff, do you use 520 chain/sprockets? Little bit to be gained there, even opt for non o-ring chain
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Post by jon on Feb 13, 2022 14:51:59 GMT 1
Part of my reasoning is that I happen to have 3 really good standard sets that have been kept together. Minimal rotational play, good basket fingers and spot on tolerance marks.
I’d like a billet basket and so pulling one of these apart is a bit of a shame. There probably worth around £100 for a good set these days, and that would put money towards building a straight cut set from scratch.
Perhaps I’m over estimating what it would bring, but I put an uprated straight cut set in a highly tuned Vespa once, and it transformed the power delivery in terms of increased torque.
Jon
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Post by jon on Feb 13, 2022 14:54:09 GMT 1
I never bothered on mine, just used the standard helical gears Know what you mean about gearing, I've got 17/41 with 17 inch wheel and it's under geared I have a 39 to go on the rear which I haven't tried but I may just buy an 18t offset front sprocket Steve I’ve already bought a 17 tooth offset sprocket, and the 39 tooth sprocket I have machined is bespoke in its offset. I know I could change these, but that would be another extra expense. Jon |
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Post by midlifecrisisrd on Feb 13, 2022 15:28:38 GMT 1
With a 39t rear it should be fine
Its just that first is low and it revs Its nuts off on the motorway with the 41t
Yes 13mm is lost off the diameter but a 110/80 is 88mm wall and a 140/70 is 98 wall so nothing in it overall against standard
On the 41t mine is about 115 on the red line (dyno measured)
Your other option is banshee 1st and 6th. First is taller and second slightly taller
Got a couple of this set up for my next builds
Steve
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Post by Tobyjugs on Feb 14, 2022 15:00:34 GMT 1
I never bothered on mine, just used the standard helical gears Know what you mean about gearing, I've got 17/41 with 17 inch wheel and it's under geared I have a 39 to go on the rear which I haven't tried but I may just buy an 18t offset front sprocket Steve I've tried allsorts of gearing on my 400cc engine and ended up with the 17/41 using as set of Nova primary gears. I liked the combination as top speed was enough and I prefer the acceleration. The same engine is now running with the dry clutch the straight cut primary gear ratio is 2.53/1 with 16/41 sprocket set up. This is woefully tall. I don't have a Speedo but I estimate around 80 mph for 6.500 rpm. |
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Post by jon on Feb 15, 2022 18:50:09 GMT 1
In the real world I doubt they make an appreciable difference, however on paper they sound good. I’ve already mentioned I think it would be a sin to replace the basket on a perfectly good gear set. However I’m thinking the superfinishing will reduce drag helping power and less wear, and the side loading on the crank be eliminated.
I know I could achieve overall gearing with sprockets, but I wonder if doing this at the clutch will increase torque in the power curve?
I intend to fit an 8 plate capable basket, so if in the future I decide I want 8 plates the inner basket change would be a quick and easy swap. I’ll start with 7 plates and wider frictions.
Jon
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Post by Tobyjugs on Feb 15, 2022 21:46:48 GMT 1
In the real world I doubt they make an appreciable difference, however on paper they sound good. I’ve already mentioned I think it would be a sin to replace the basket on a perfectly good gear set. However I’m thinking the superfinishing will reduce drag helping power and less wear, and the side loading on the crank be eliminated. I know I could achieve overall gearing with sprockets, but I wonder if doing this at the clutch will increase torque in the power curve? I intend to fit an 8 plate capable basket, so if in the future I decide I want 8 plates the inner basket change would be a quick and easy swap. I’ll start with 7 plates and wider frictions. Jon Even with straight cut primaries a new crank shaft was pulled open. More to do with the rpm or possibly crankshaft quality. |
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Post by midlifecrisisrd on Feb 15, 2022 22:09:16 GMT 1
Surely the helical primary can't spread the crank if the RH bearing is good
Only side slop in a worn bearing would allow this
Steve
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Post by Tobyjugs on Feb 15, 2022 22:18:38 GMT 1
Surely the helical primary can't spread the crank if the RH bearing is good Only side slop in a worn bearing would allow this Steve I think it's more to do with oscilation and high rpm. The crank shaft in my 400cc engine has been out of phase which i put right then it started spreading so i pressed it back and got the pins welded. It's still good now but hasnt been so badly mistreated as the other. |
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Post by jon on Feb 15, 2022 22:28:17 GMT 1
As standard the bearings are ball race. These quickly wear out with side thrust. New ones with our limited milage are probably fine. Tz’d used roller bearings and straight cuts.
I’m using 10 ball roller bearings so am keen to take any side loading off them as they are more suitable for compression loading.
Jon
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Post by jon on Mar 22, 2022 20:04:37 GMT 1
Another thing I’ve read but don’t know how true it is is that the +7% gear kits take torque of the clutch meaning it is less likely to slip?
I’m struggling to work out if this is the case or the opposite?
Anyone else agree?
Jon
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Post by jon on Mar 22, 2022 22:30:14 GMT 1
Surely the helical primary can't spread the crank if the RH bearing is good Only side slop in a worn bearing would allow this Steve Bearings with a groove and clip are less likely to allow side movement, but TZ or o ringed bearings without a groove are more prone. I have a hot rods crank with 10 ball rollers with o rings. That’s why I’m keen to avoid any side thrust. Jon |
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Post by muttsnuts on Mar 24, 2022 10:24:02 GMT 1
Surely the helical primary can't spread the crank if the RH bearing is good Only side slop in a worn bearing would allow this Steve Bearings with a groove and clip are less likely to allow side movement, but TZ or o ringed bearings without a groove are more prone. I have a hot rods crank with 10 ball rollers with o rings. That’s why I’m keen to avoid any side thrust. Jon be sure to use the clutch side locator half moon retainer plate with the hot rod crank, if that bearing has an O ring on it, just remove the O ring and use the retainer. On the bigger power engines I also groove the crank case for one of the centre bearings and use another locater/retainer plate, that seems to solve any "bearing" walk HTH |
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