Yamaha RT1 crank pin and bearing.

[firko]

I've made a startling discovery that's stopped me in my tracks.
I'm currently building a new 360 RT1 motor for my flat track Hindall to go with the 250 I've already built so I can change engines whenever I feel the need for a class change.

Well....I've got 2 new 24mm crank pins (214-11681-00-00)  and bearings (93310-52478) (which are listed for the DT1 RT2 DT3 etc) and a NOS 214 rod and a Prox rod in identical dimensions (the other's intended for my Cheneys impending upgrade).
My problem is that yesterday I took two cranks to Frank Stanborough to build and balance them for me and upon pulling them apart discovered that they've both got 25mm crank pins yet they still have the same 214 rod. My questions to my Yamaha comrades are.....

When did they make the change from the 24mm to 25mm pin or was it visa versa?
How can the same # 214 rod be used with different sized crank pins?
I presume the difference must be in the bearing, if so what is the number? I can't find anything other than the 11681 24mm pin or 52478 bearing.
What are the pin and bearing part numbers needed for the 25mm pin flywheels.
Can I still use my new 214 and Prox rods?
Does anyone have the needed (new) pin/bearing they'd like to sell me?
If not, where can I find one?

I've been fiddling with these engines for a long time but this is the first time I've come accross this difference. It's cool finding out new things but this is a pain in the arse as I need to get at least one of these cranks done so I can get the Cheneys 360 motor to Lozza for the next stage in it's development. The tracker motor has less priority as I already have a fresh 250 ready to go.

[vandy010]

i have no idea as to the correct answer but when i did the crank on my MX250 i was also caught out by 24mm v's 25mm crank pin issue.
i can't remember what i had but it was a trip back to Yamaha for the alternate part and my machinist dude made it all happen.
t'was but a Yamaha part number mystery...

[firko]

Bill Davis from Texas PM'd me with an interesting take and cure of my problem. I'm sure you early Yamaha guys will also be interested in his reply so I'm sure he won't mind me posting it here. Bills been helpful with my DT1/RT1 info and parts in the past. He's also the guy supplying Peter Lee with his DT rides in the US later this year and has raced a couple of times in WA over the last few years. He's a good bloke.
Firko!!
I only ran into this one time on an early DT1.I ended up finding a later model crank.I'm not sure on the Yamaha Part numbers or when they made the change.I think you're probably right that if you could find the right pin & bearing,you maybe could use the rods.You may want to check the rods and make sure they are slotted for lubrication and not just having a small round hole to get oil to the bearing.Early ones with the hole were prone to problems.
I normally use A/M rod kits for a 83-89 Yamaha YZ 250.They work fine,use just have to use a 83-89 YZ 250 top end bearing as they are 1MM larger outer diameter.You usually can get these kits reasonably priced.This bigger top end bearing is also use on the YZ 465 & 490.
My YZ 250 parts list shows the pin you need is 275-11681-00,and bearing is 93310-42584.
http://www.nwvintagecycleparts.com/search-results.php?q=93310-42584&st=spart&search.x=10&search.y=17
Northwest Vintage Cycle has bearings for 35.16 each but no pins.
I used to find rod kits for about 50.00 on Ebay but haven't looked in a couple of years.
Hope this helps.Keep me posted

[Freakshow]

we covered this a while back in a thread Firko, as i went throught the same issue, which then leads on to the 5mm barrel problem.
only the DT1 uses the 24mm pin, YZ and RT1 use the 25mm, the differances are in the bearings as the crank inner is the same size on both. as is the small end.  As your mate says if you use the later Rods or the A/M you need to hunt down the bigger bearing size 20mm bearings for the top end and so on.
without going to get my list im prity sure i have the info.

I bought up a stack of 24 and 25mm pins and both crank bearings, id have to hunt them out to see if i have any spares, i rebuild 4 last year and have 2 yz i want to do this year.  also if you already have 25mm cranks then you cant put the 24mm pins in them) and if your going to use them webs then your already going down a certain path.

What rod you use will depend on what barrell you are putting on it and what piston your using.  there are plenty of rods that interchange like the 313 and the 24Y so the ROds not your issue.
What prox kit have you got  there ?  Email me might be easy, and ill dig out my notes