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Post by midlifecrisisrd on Jun 16, 2020 16:03:27 GMT 1
Not got an LC manual and building an engine
Figured my ypvs manual and a parts pdf would be enough but got a question
Is the backlash of 155 the same?
Something in my head says lower but that may just be the number ranges I'm thinking about 🤔
Steve
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Post by darboots on Jun 16, 2020 16:10:25 GMT 1
From the Yam WM for the 350LC / 250LC -
Primary drive gear backlash number - 65 to 69
Primary driven gear backlash number - 62 to 66
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Post by midlifecrisisrd on Jun 16, 2020 16:19:03 GMT 1
From the Yam WM for the 350LC / 250LC - Primary drive gear backlash number - 65 to 69 Primary driven gear backlash number - 62 to 66 But what's the total Steve |
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Post by darboots on Jun 16, 2020 16:23:54 GMT 1
From the Yam WM for the 350LC / 250LC - Primary drive gear backlash number - 65 to 69 Primary driven gear backlash number - 62 to 66 But what's the total Steve Seems to indicate (65+62) 127 to (69+66) 135 It's not given specifically.
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Post by midlifecrisisrd on Jun 16, 2020 16:28:40 GMT 1
But what's the total Steve Seems to indicate (65+62) 127 to (69+66) 135 It's not given specifically.
Cheers bud Would seem to indicate 131 +/-1 then Thanks Steve |
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Post by dusty350 on Jun 16, 2020 16:48:06 GMT 1
Mmmm, all models of Ypvs use a 4l0 primary drive gear. Those gears are often high 80's to mid 90's numbered. I thought the Lc backlash figure matched the Pv's ? The aircooled 400 backlash is 131 +/- 1. You can use an Lc basket and gear in an ac, but not the primary drive ( well, not without a lot of work £££) Dusty  |
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Post by midlifecrisisrd on Jun 16, 2020 16:51:33 GMT 1
Mmmm, all models of Ypvs use a 4l0 primary drive gear. Those gears are often high 80's to mid 90's numbered. I thought the Lc backlash figure matched the Pv's ? The aircooled 400 backlash is 131 +/- 1. You can use an Lc basket and gear in an ac, but not the primary drive ( well, not without a lot of work £££) Dusty See this is where im getting confused and the lack of manual isn't helping I thought ypvs primaries were high 80's to mid 90's LC were low to mid eighties The clutch baskets are the same parts so technically should still be 155 but I'm not sure Steve |
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Post by dusty350 on Jun 16, 2020 17:03:34 GMT 1
But if you ordered a primary gear for any model of Ypvs, you would quote part no. 4l0 16111 00 which is 350lc. The primary drive/backlash question is one that causes all sorts of head scratching ! Dusty |
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Post by oldelsieboy on Jun 16, 2020 17:05:30 GMT 1
From the Yam WM for the 350LC / 250LC - Primary drive gear backlash number - 65 to 69 Primary driven gear backlash number - 62 to 66 But what's the total Steve The LC Factory Manual is wrong, it does state 131 +/- 1 but should be 155 +/- 1  OEB |
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Post by dusty350 on Jun 16, 2020 17:06:47 GMT 1
Just to add to the confusion, the Lc clutch basket is a different part number to a Pv basket, so something is different ? Dusty |
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Post by dusty350 on Jun 16, 2020 17:07:59 GMT 1
As I typed my last reply, I did think we should just ask you Nigel  The font of all Lc knowledge Dusty |
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Post by dusty350 on Jun 16, 2020 17:12:37 GMT 1
And just as well it's 155 coz that's what I've built all my Lc engines to !! |
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Post by oldelsieboy on Jun 16, 2020 17:29:56 GMT 1
Just to add to the confusion, the Lc clutch basket is a different part number to a Pv basket, so something is different ? Dusty Not any more, order a 4L0 basket & you will receive a 31K item. And the primary gear for both an LC & YPVS have a 4L0 part number. Seem to remember reading someone suggesting that the difference between LC & YPVS baskets were the sizes of the cush rubbers, odd sized fitted to an LC & the same size to YPVS  OEB |
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Post by flames on Jun 16, 2020 22:43:58 GMT 1
forgive me if this is a stupid question but what is backlash and what is good / bad about it?
I mixed parts from different spares i had at the time and just fitted the parts that looked in the best condition. Now wandering if i need to pull apart and check some stuff i didnt know needed to match.
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Post by 4l04ever on Jun 16, 2020 23:21:29 GMT 1
The LC Primary Drive gears usually have a backlash from around 88 to 95. Total should add up to 154, 155, or 156.
The purpose is to get the correct clearance between the primary gears. If one gear has slightly larger teeth, then the other must have smaller teeth to compensate.
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Post by darboots on Jun 17, 2020 6:01:44 GMT 1
I got the info direct from Xavier's site - rd350lc.net/pageWM.htmSo, in light of the above comments, and having to use PV primaries, as OEB says, the Yamaha WSM is wrong! |
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Post by dusty350 on Jun 17, 2020 7:58:06 GMT 1
Backlash often gets talked about on here. It relates to the clearance between teeth on gears as they mesh together. If there was zero clearance they would grind and chew, heat would build up with friction and probably lock up or break teeth. Too loose and they will whine and be noisy in use. The correct backlash will allow gears to mesh together properly, allowing oil to penetrate between the teeth as they mesh, lubricating and cooling. Different engines will have different backlash figures. Our bikes will have a number etched on the primary gear, and the primary driven gear on the back of the clutch - the 2 numbers added together should achieve 155, with a tolerance of 1 each way, so 154 or 156 is acceptable too. In the Rd400 engine I've just built, the backlash should be 131 +/-1, so different models will have different numbers. What we cant account for is 40 odd years of wear, and how that may affect the original tolerances ? The best thing to do when rebuilding any engine is to try and match gears so you achieve the intended backlash, so you will find "wanted" ads for primary gears with a certain number engraved on them as guys try to achieve it. Dusty |
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Post by Tobyjugs on Jun 17, 2020 12:41:54 GMT 1
After measuring quite a few backlash combos I can't find a direct relationship purely to do with tooth clearance and higher or lower lash numbers.
I have always stuck to the 155 protocol.
I think it might be something to do with the helix angle at which the gears are cut and the contact patch.
I have 2 sets of straight cut gears.
The clearance on these sets are 0.2mm and 0.24mm.
The average clearance I've measured on standard primaries is 0.12mm. There is one set in use with an average of 0.08 mm. This engine has covered just over 11,000 miles with no signs of deteriation on the primaries.
Beat me what it stands for.
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Post by dusty350 on Jun 17, 2020 15:20:16 GMT 1
When I stripped my 430e clutch recently to check the numbers, they were way out from the 131 Yamaha intended  But, it's been running with the mismatched gears since at least 1986 and there has never been any issues or problems related to the gears. It sounds like all the other aircooleds I've had, no swarf in the oil, no blued teeth or bad witness marks from poor meshing. But, I agree with Tony, get the magic number if at all possible Dusty |
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Post by flames on Jun 17, 2020 17:42:44 GMT 1
Cheers. Will get mine stripped and checked before she is built.
If I make sure I do everything properly this time around, I might actually get her built, looking half decent and more than a little reliable.
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Post by veg on Jun 17, 2020 17:47:54 GMT 1
Flames I’m with you it’s right over my head, and tbh when Steve is talking about back lash I always wonder what’s he said now?
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Post by midlifecrisisrd on Jun 17, 2020 17:52:54 GMT 1
Flames I’m with you it’s right over my head, and tbh when Steve is talking about back lash I always wonder what’s he said now? That's too funny 😆 Steve |
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Post by midlifecrisisrd on Jun 26, 2020 20:21:32 GMT 1
I need to make a decision on this 🙄
Opened 2 lc engines and neither added to 155 ☹
Spoke to the guy I get a lot of my parts from and he said he has never opened an LC engine and found 155
He says they are usually low to mid 140's
I just bought basket from a ypvs that is a 62
Now have primary 79, 86 and 94
So what to use?
141, 148 or 156
My head is bust 🤯
Steve
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Post by dusty350 on Jun 26, 2020 20:41:12 GMT 1
Hi mate Why not go with 156 ? It's in the range. Yogi gifted me a Pv clutch to make the magic number with my Lc primary. Would have quite happily used it in my 400 until I realised the amount of work needed to mod the primary gear for a recess, but you should be fine. Dusty |
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Post by midlifecrisisrd on Jun 26, 2020 20:47:33 GMT 1
Hi mate Why not go with 156 ? It's in the range. Yogi gifted me a Pv clutch to make the magic number with my Lc primary. Would have quite happily used it in my 400 until I realised the amount of work needed to mod the primary gear for a recess, but you should be fine. Dusty I've just tried that Thought that might be the way to go but when I fit them I get 2 tight spots When I fit the 86 which gives 148 they aren't there 🤔 Steve |
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Post by dusty350 on Jun 26, 2020 20:52:04 GMT 1
Well, that changes everything !! My 430e is out by a fair amount and its fine, but I spose it could be loose rather than tight with my gears. If you can feel binding I wouldn't use that particular gear. Dusty |
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Post by lb on Aug 18, 2020 10:45:30 GMT 1
I need to make a decision on this 🙄 Opened 2 lc engines and neither added to 155 ☹ Spoke to the guy I get a lot of my parts from and he said he has never opened an LC engine and found 155 He says they are usually low to mid 140's I just bought basket from a ypvs that is a 62 Now have primary 79, 86 and 94 So what to use? 141, 148 or 156 My head is bust 🤯 Steve Lol so Steve what was your outcome as I'm in same boat myself now... |
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Post by midlifecrisisrd on Aug 18, 2020 11:11:24 GMT 1
I need to make a decision on this 🙄 Opened 2 lc engines and neither added to 155 ☹ Spoke to the guy I get a lot of my parts from and he said he has never opened an LC engine and found 155 He says they are usually low to mid 140's I just bought basket from a ypvs that is a 62 Now have primary 79, 86 and 94 So what to use? 141, 148 or 156 My head is bust 🤯 Steve Lol so Steve what was your outcome as I'm in same boat myself now... Think I fitted the 148 as that had no tight spots and fealt exactly the same as the 141 Steve |
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The font of all Lc knowledge 
But, it's been running with the mismatched gears since at least 1986 and there has never been any issues or problems related to the gears. It sounds like all the other aircooleds I've had, no swarf in the oil, no blued teeth or bad witness marks from poor meshing. But, I agree with Tony, get the magic number if at all possible 
