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Discussion Starter #21
It really blows me away that an XL250 would be on the list , being I have one and it was right under my nose , but mine is a earlier year , but close , from what I have researched on my XL250 , I believe the difference would be the early production XL250's had the SL250 engine in them, they were called MotorSports ------- this sprocket being interchangeable makes me wonder what else could be interchangeable , like maybe sticking a SL250 MotorSport jug sleeved up and upper or even a 500 jug and upper onto a 300 lower , but would think the jug bolts would not line up as with a 500 they would need to be a bigger spread ----just dreaming out load
Your 250 has the early design sprocket like you thought fishfiles... none of the newer part number sprockets will fit.
 

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Discussion Starter #22

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Discussion Starter #23 (Edited)
I wonder how much Remthal chainwheels would charge to cut a batch of say, 10. If I made an enquiry and the price was right would anybody be interested?
Might be cheaper to buy a bundle of these with a bulk discount:

https://www.partzilla.com/product/honda/14321-KB4-671

and chuck them up in a lathe to machine .090" out of the inboard side for the mounting flange... The forging is identical in diameter, pitch and width (6.4mm = .252") it just needs the flange area cut to move the centerline back in .090" where it belongs.

These were installed in CMX250C Rebel motors through 2009, so they should remain cheap and plentiful for a few more years.
 

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Discussion Starter #24
@mac102004 you should do a thread on big bores for 300’s your very knowledgeable in that field I have to say, maybe @retro or @shadetree would sticky it for future reference?
I 2nd that idea! It would get stickied alright... whaddya think mac102004?

I'd like to see your solution for the two extra head bolts, fitting the 500 head to the 350 jug casting. I'm not sure how I'll handle that yet.
 

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Do you think .090” would matter on a chain retro? That’s minuscule isn’t it.. I know it should be smack on centre but forgings could be out on an old motor by that much couldn’t they. On another note though, if anybody does want to go that route, post me your chain wheel and I’ll put it in the lathe for you, for free of course.
 

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Discussion Starter #26
Well, .090" doesn't sound like much considering the long chain length and distance between sprockets, but its enough to ruin the cam chain real quick. The upper sprocket centerline has to be directly in line with the lower sprocket center to allow the chain to become loaded on a single plane (straight pull) only. You might get away with +/- .005" max would be my guess, judging by the DID chain I have... but I wouldn't even allow that much on a high RPM motor. The chain link pins would be stressed and wear very quickly. The chain links might also rub and chew up the edge of the sprocket teeth due to such misalignment.

Endplay on crankshafts and cams rarely exceed a few thousands inch, even when worn completely out. So once the sprockets are set up correctly they should stay set up for the life of the motor.

FYI, there are some used sprockets for sale on the fLeebay with shiny/worn edges on teeth on one side. If I can find some again I'll post them... obviously Honda missed the setup on those motors.
 

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Very true. Speaking of cam endfloat/play it could cause wear on the cam seats and increase endplay couldn’t it.
Yeah post them on here, it’s a long way to ship but as I said I’m able to machine them down here if anybody needed that service.
 

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Wow , you have been busy last night -----Honda called and they want to hire you as an engineer ! -------- I put the 428# on e-bay and got some hits >
 

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@mac102004 you should do a thread on big bores for 300’s your very knowledgeable in that field I have to say, maybe @retro or @shadetree would sticky it for future reference?
I 2nd that idea! It would get stickied alright... whaddya think mac102004?

I'd like to see your solution for the two extra head bolts, fitting the 500 head to the 350 jug casting. I'm not sure how I'll handle that yet.
I kind of came to the conclusion awhile ago that fitting the 500 head onto the 350 cylinder and bottom end wasn't really worth the effort, I think your time would be better spent putting bigger valves in the 350 head and porting it. Just use the 500 sleeve in the 350 cylinder and use the 350 head. It's not ideal, honestly the 500 piston would be better suited to the 500 head and combustion chamber, but I guess you can't have your cake and eat it too. You could have a custom piston made for the 350 head in the larger bore size though, I know CP will do small batches of 2-3 pistons.
 

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Discussion Starter #30 (Edited)
I noticed while comparing another candidate sprocket (a 14321-KF0-000, it failed to match) with the others that my NOS 14321-HA0-010 differs from the same part number sprocket that I took out of my 87 350D. So I cut open the NOS package and took it out for measurements and photo comparison.

This is an info update along with a couple photos to show differences in appearance of the three interchangeable sprocket part numbers I have on hand so far... and I'm finding some variations or revisions of each part number installed in the various motors. I'm not 100% positive yet, but it appears that Honda may have used all three part number variations during factory assembly, both on 250 and 350 motors. I know that sounds weird, but I'm finding -428- sprockets mounted on 250ES cams... and my two -HA0- sprockets I have on hand differ quite a bit from each other.

I also updated the first post in this thread with some additional info and will be adding a link to that first post for these photos.

This first photo shows the outboard side of three sprockets. (On the left is a new NOS 14321-HA0-010, Center is a used 14321-428-000, Right is a used 14321-HA0-010)

Note that the smaller .280" diameter top mounting hole is not marked with a dot (.) on the -428- and the used -HA0- on the right differs from the new NOS -HA0- on the left which has a set of outboard-side timing marks added onto it:



The same three sprockets flipped over to show the inboard side of each.
The used -HA0- on the right looks more like a 250ES sprocket than a 350D, doesn't it? The new NOS -HA0- on the left is made stronger than the used one and is almost as heavy as the -428-:



There appears to have been some mixing and matching of these sprocket forgings through the years. The search continues...
 

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