Vintage Dirt Bike Q & A

ive been stripping the part restored MT250 I recently got and it seems it was done some time back and then the owner just stopped work so some parts were cleaned and have now rusted and some are still perfect etc. A real mixed bag.... anyway, all was going well until i realised the previous owner had buried his head in the sand when he got to the swing arm pivot... hmm... not only was the collar rusted in place but even the bolt was hard to remove, although it looks ok now its out, phew! In the past ive had to replace worn bolts as when everything else fails they pivot on the bolt and trash themselves, eek. Anyway, I need a new collar and new bushings...

So... Whilst ive been looking for the bushings and collar for the bike Ive found that if I use the online parts books on CMSNL and BikeBandit I get what looks like a different swing arm than the one I have. I assume the ones online are the USA models and have slightly different parts to the Aussie models, and whilst most are the same, there are a few differences.

The swing arm in the pics has no mounts for passenger footrests, and a grease nipple on the top of the arm, but my Aussie swingarm has footrest mounts welded on the grease nipple on the end of the swinger bolt. Both my bikes are the same and have the same setup so it must be factory.

I would be totally ok to order the collar and the bushings from the online parts numbers if they were the same parts for all years and I would just assume the pics were 'generic', but there are two different types of these parts it seems. hmm... the earlier models used a different collar and bushings than the later ones... and so I dont know which parts I have... hmm...

Upto Serial#: 1031049 seems to have part number 52109-358-006 for the bush but the fiche also lists 52108-457-300 which is the same as the later version, perhaps this is the same thing the other Hondas of the 70s had where the original was a plain steel bush with felt washers, but if so then i'm surprised the felt washers dont show on the parts diagram, although it does say there are differnt caps to fit the earlier bushes... hmmm... The two collars are: early: 52141-357-000 & later: 52141-358-770 Anyone know what the difference in those parts is? I would assume if one was for the earlier felt washer cup then it would have been a shorter collar than the later one, but im not sure, and of course i dont know what the length of either really is...



.... hmm.... Does anyone have any swingarm parts they can measure from a US spec bike so I can be sure of what Ive got?

(what follows was measured with a caliper, but of course there could be inaccuracies of a new 0.1's as the caliper arms are flat not ridged and also the parts have worn a little)

The collar I have is:
OD (could have worn a little): 21.4mm
length: 182mm (could be 183?)
ID: 14.3mm

The 'plastic' (look original) bushings I have are:
OD of body: 26.4mm
OD of flange: 32.5mm (hard to measure as flange is trashed)
ID: 21.7mm
length: 44.7mm

I was hoping I might find the bushings to be the same as the ones people have recently had made in bronze for the CB and other models as I dont want to refit the original honda 'plastic' type units, assuming i could find some. I read that the CB450 has three types of swingarm bushings but that the Honda parts measure about 43mm long x 22mm id x ~26.5mm od, he said that he didn't have a really good caliper, 'so there's not machinist-like accuracy in those numbers'. But they seem close to what im looking at... if so that means the bushings are part number: 52108-457-300 which means I have the later version parts in the online parts books...

(more info here on the bronze bushings: http://www.hondatwins.net/forum/viewtop ... f=21&t=448 )

I also would like to find another collar as mine is pitted, but dont want to punt in the dark with this as they are hard to find and im bound to end up with the wrong one, hmm....

Id really appreciate any help and measuring you guys could do for me on this, and of course if anyone has an Aussie parts book Id love a copy as it would make my life a little easier, Thanks guys!

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MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

If you like watches, check out my websites: DeskDivers.com & PloProf.com

Looks like ive answered my own swingarm question as there was a guy selling one of the collars NOS on ebay, he didnt want to measure it for me like it was some sort of secret info he is holding, but said he would compare my measurements with what he had, his answer was 'NOT SAME SIR'... Hmmm.... useful...ish.... I dont know if its like 0.1mm out or something and hes just being pedantic

My real measurements for my collar are:
- Length = 18.34mm
- Outside diameter of ends = 21.3mm
- Inside diameter of ends = 13.9mm

So, taking him at his word (not ideal i know, but no one else seems to know any better), since his part was honda part number 52141-357-000, that should mean that the Aussie version needs the other one, ie 52141-358-770... I see a few places that list them, so its just a case of getting one now. If anyone have one they wont use then i would be interested of course.

_________________
MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

If you like watches, check out my websites: DeskDivers.com & PloProf.com