[retro]

The following Honda 38T cam sprocket part numbers are bolt-in interchangeable. Each are also known to fit all Fourtrax TRX300/TRX300FW motors when swapping in a ATC250ES/250SX or Fourtrax TRX250 camshaft (14101-HA0-000) and cam chain (14401-HA0-003).

Honda part number & year/model fit:

14321-HA0-000
1985 ATC250SX
1985 ATC250ES
1985 TRX250
1985 ATC350X

14321-HA0-010
1985 ATC350X
1986 ATC250ES
1986 ATC250SX
1986 TRX250
1986 ATC350X
1986 TRX350
1987 ATC250ES
1987 TRX250
1987 ATC250SX
1987 TRX350
1987 TRX350D
1988 TRX350D
1989 TRX350D

14321-428-000
1978 XL250S
1979 XL250S
1979 XR250
1979 XR500
1979 XL500S
1980 XR250
1980 XL500S
1980 XL250S
1980 XR500
1981 XL250S
1981 XL500S
1981 XR250R
1981 XR500R
1982 FT500
1982 XL500R
1982 XL250R
1982 XR250R
1982 XR500R
1983 FT500
1983 XL250R
1983 XL250R

I bought a used 14321-428-000 XR500 cam sprocket off from a seller on the fLeebay for this comparison with a worn out 14321-HA0-010 cam sprocket from a TRX350D. I felt confident when I risked a few $$$ on it that it might match up well with a 14321-HA0-010 but to be honest, its an even better match than I hoped for. It is a strong, very well made sprocket. I like it so much I'll probably swap an NOS one (if I can find one) into my 350D motor while its down for rebuilding.

Thickness of the two forgings measure identically at .250" The overall diameter and the pitch are identical. It weighs 10 grams heavier (101gm vs 91gm) having a .020" thicker cam attachment flange machined in and the forging has full-width teeth which an aftermarket D.I.D. TRX350D cam chain fit very nicely over, with chain links end play to spare. Those full-width teeth allow chain links more contact area on the outer edges of the sprocket while further enhancing the chain fit.

The outboard side of the -428- forging is unmachined, whereas the -HA0- sprocket has .010" machined out of it. On the inboard side of the flange the -428- is machined to .090" depth while the -HA0- is machined to .100" depth, which partly explains the -428- sprockets' .020" thicker attachment flange. Sure this lil' bugger weighs 10 grams more, but stability will be much improved and chain life should be extended as well, due to meatier teeth/full contact profiles.

Looking at the figures above we notice .010" difference is unaccounted for between the two identical thickness forgings. Well, that .010" was machined out of the -HA0- sprocket on the inboard side (just the sides of the teeth only, leaving a narrow band) which results in a narrower load handling area for the chain. In effect, Honda apparently took a -428- forging, weakened it, then slapped a -HAO-010 part number on it.

The -428- sprocket also shares the same centerline with the -HA0- once it is bolted to the camshaft, so its centerline hovers over the crankshaft sprocket centerline perfectly.

Installation Notes (updated):
The two sprocket mounting bolt heads will be rotating .010" closer to the head & rocker box castings when assembled. This should not be an issue on any motor since there is plenty of space available on all heads this sprocket fits. Normal camshaft endplay is very well controlled using the stock cams. But do verify that both bolt heads clear the castings with room to spare if you use the -428- sprocket. You can get that .010" back by grinding off the outer ring on the hollowed out mounting bolt heads if needed for your application.

All three part numbers have the same two mounting bolt holes drilled in them and one hole is larger than the other. One bolt hole (the uppermost hole when the cam is being installed properly, with lobes facing down) is about .280" diameter and is marked with a dot (.) on the outboard side of -HA0- sprocket part numbers. There is no outboard side dot (.) on the -428- sprocket forging identifying the smaller diameter .280" mounting hole.

The opposite (lower) mounting hole in each and every sprocket part number measures about .292" diameter.

So, the smaller diameter mounting hole should always be up when installing the sprocket onto the cam, whether that hole is marked with a dot (.) or not.

Also note that there may be more than one variation/revision of each sprocket part number found in various stock motors and NOS packaging. They may have been purposely interchanged on Honda assembly lines, because I see both -HA0- and -428- style sprockets that were bolted onto 250ES cams for sale on the fLeebay. I also have an NOS -HA0-010 that differs in appearance from the stock sprocket that was installed in my 87 350D... the one installed by the factory looks like a 250ES sprocket. Weird.... but since all three sprockets are identical except in appearance and outboard side markings (and slightly narrower tooth-tip radius machining on some of them), why not...?

Link to post and photos showing differences is HERE.

Conclusion:
Every one of these sprocket part numbers are identical-fit interchangeable, with the -428- being the most durably made sprocket of them all.

 

[retro]

Next attempt:

DIY 14321-KB4-671 cam sprocket interchange with all of the above part numbers. This should take just a few minutes on the lathe to make it fit.

The 14321-KB4-671 sprocket is readily available and cheap, so if we can pull this one off...

Watch this thread for more!

EDIT: The Partzilla interchange list for this sprocket part number is incomplete. This sprocket & part number was used through 2009 on all Honda CMX250C Rebel motors, which means it should be available for several more years at a cheap price.

https://www.partzilla.com/catalog/honda/motorcycle/2009/cmx250c-a-rebel/cam-chain

 

[SamUK]

Good job retro, very informative as per usual. Wants making a sticky IMO.

 

[shadetree]

Good job retro, very informative as per usual. Wants making a sticky IMO.

done !!..lol..ask..( be nice ), and it shall happen !..lmfaooo.

 

[shadetree]

Good job retro, very informative as per usual. Wants making a sticky IMO.

and why the freak are you up so late ?..ya bored ??!!..lmfao.

 

[SamUK]

Good job retro, very informative as per usual. Wants making a sticky IMO.

and why the freak are you up so late ?..ya bored ??!!..lmfao.

Haha.. it’s 06:50 here in the UK, I start work in 10 minutes... wakey wakeyyyy!! Lol

 

[shadetree]

Good job retro, very informative as per usual. Wants making a sticky IMO.

and why the freak are you up so late ?..ya bored ??!!..lmfao.

Haha.. it’s 06:50 here in the UK, I start work in 10 minutes... wakey wakeyyyy!! Lol

lmao, I haven't slept yet, just watching the forums for outlaws..seems I found you !..lol. check out my shadow thread, I updated it.

 

[fishfiles]

Wow , great work , I know some people that will love to know this information !

 

[SamUK]

@retro it seems people are listing the TL250 the same as the XL250... two OEM parts here on eBay if they match up..


https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/202088597657

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/162072877423

 

[fishfiles]

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

 

[mac102004]

Interesting. Pretty hard to find any of these sprockets new anymore. I found a 428 on the other side of the world, about $75 CAD.

 

[fishfiles]

Sam , Ero = e-bay

https://www.ebay.com/itm/Pignone-ca...037927?hash=item2a92a6e667:g:lK0AAOSwWxNYr1a0

 

[fishfiles]

Mac , I know you are most probably the most knowledgeable on motor mods , have you heard of any other 300 mods using different uppers , cranks or rods , other than 317 , 355 or 380 ? when they put the 350D head and jug on a 300 lower , what does that one come out to be cc wise

 

[SamUK]

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?

 

[mac102004]

Mac , I know you are most probably the most knowledgeable on motor mods , have you heard of any other 300 mods using different uppers , cranks or rods , other than 317 , 355 or 380 ? when they put the 350D head and jug on a 300 lower , what does that one come out to be cc wise

317 is more of a modern build, 355's have been around a long time, the 380's now aren't the same as the old ones I don't think, Thumper Racing used to do a 372cc? that was called a 380 but these new 380's are true 380cc. So the 355 and 372 (380) were kind of the most common in the past. These were all just custom sleeves and pistons rather than using something out of another machine like the 317 kits. I have a few more idea's for top end swaps, some have been done, some haven't as far as I know.

Complete top end swaps were always either the 300EX or the 350D, neither of which being very common due to the work involved. I really don't know much about doing the 300EX top end as I've yet to do one myself. The 350D I know a bit more about since I've done it.

The 350D top end requires the use of the 350 crank as well, so it ends up with the exact same bore and stroke as a stock 350D, 350.4cc engine. Assuming you don't do a big bore with it. It's fairly easy to just do the stock 350 top end and leave it alone, you still require the custom reverse ground camshaft but it would be an extremely reliable setup having all that cylinder wall left and the correct cylinder jug itself for that size piston. Add an oil cooler to it and it would run no hotter than a stock machine.
Wiseco makes a couple different high comp pistons in STD and oversize for it as well. I have one of these motors on my shelf right now with a STD 350 10.5:1 Wiseco in it.
Now going beyond that, you can use any big bore kit for the TRX350 or ATC350X provided you can find one. Custom you could do an XR500 piston and sleeve in the 350's cylinder, this would require some spacers on the base of the cylinder however and you'll probably want to take some off the dome of the piston if you're going with an aftermarket high comp piece. Stock bore on the XR would be 89mm so 89x68 gives you 423cc. They sell oversize for that as well, 90, 91, 92mm IIRC, maybe even 93mm? 90mm would give you the same bore and stroke as a 450 Foreman, 432cc. I have another 350 cylinder sitting here with an XR500 sleeve and bored for a 90mm piston, I just have to either take some off the dome of it or maybe look for a stock compression 90mm piston instead, not sure haven't touched it in a long time.
They do make a 95mm big bore for the XR which would give you 482cc provided you can fit a sleeve that big in the bottom end. As it is there is some pretty extensive case boring required to fit the standard XR500 sleeve.
Really the BEST bet on a big bore for that style motor would be to find one made for the 350, but they are not as easy to come across as the 300 big bore kits.

As far as those 300EX top ends go, you would probably have better luck finding big bores for those. The 330cc kit as always extremely popular and very cheap. The crank wouldn't need to be changed for the 300EX top end but you would still need the reverse grind cam. I don't know what else is involved, I thought someone had said one time that there was some issue with the cam chain length but, like I said before I really don't know. I'd love to get my hands on a 300EX top end or whole motor just to play with it a little bit and figure some stuff out.

 

[SamUK]

@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?

 

[retro]

Good job retro, very informative as per usual. Wants making a sticky IMO.

and why the freak are you up so late ?..ya bored ??!!..lmfao.

I been working all day everyday in a rush to get my pre-winter preps done. An' I ain't got a clock... LOL

 

[retro]

Wow , great work , I know some people that will love to know this information !

If Charlie and his wife (if thats who you meant?) would like to comparo those two sprockets themselves, give them my phone number so he can let me know the address I can send them both out to. Or PM me a mailing address... whatever... I got no need for them anymore.

 

[fishfiles]

Wow , very good stuff Mac , I think this one is already a sticky Sam , but a thread on 300 engine up builds would be good , 500cc on the 300 platform with 6 inch lift and a 54% reduction would be awesome for me

 

[retro]

@retro it seems people are listing the TL250 the same as the XL250... two OEM parts here on eBay if they match up..


https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/202088597657

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/162072877423

Those are pre-1978 sprockets, same that were used on the early 350 SOHC street bike motors I think? In '78 Honda changed the XL250 motor, it got a redesign matching the new 4-valve XR500 design. Those early sprockets won't interchange with our favorite motors, but I think I saw an NOS 14321-428-000 sprocket on the fLeebayUK (its in Italy) for about 30 pounds + 10 pounds shipping to the UK...? In USD the price looks too high so I didn't buy it... I'll PM you the link in case you are interested and can get it reasonably priced.