OZ ATV :: The Australian ATV Forum

[BC250R]

I've had a few people PM me about my conversion i'm doing after seeing a tease photo in the before and after thread. Watch this space for a full step by step. First up, heres all the bits you need to get from an 06 or later TRX450R. 05 or earlier will work but the swingarm is 1 inch shorter than standard.


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Last edited by BC250R on Mon May 05, 2008 5:02 pm; edited 3 times in total

[BC250R]

Heres a 5 min vid showing the completed conversion and what was done. No Speilberg but it gets the idea across


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[stitch250R]

thanks for sharing the info,excellant description, sure to save a few headaches

[BC250R]

The 450R rear set up turned out to be much lighter than the 250R. My 250R swinger is pretty heavily plated so its about a kilo heavier than a stocker. The massive reduction in unsprung weight will improve handling for sure.




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Last edited by BC250R on Tue Apr 22, 2008 5:48 pm; edited 1 time in total

[BC250R]

This is an 85 swinger next to the 06. It shows how close they are in length. The 06 is about 3 or 4 mm short of the 85. The 85 was bought as an 86 off ebay and cost me about $200 delivered. The 06 swinger can be picked up from as little as $69US for a good used item to $100US for a brand new, never riden, take off example. 30 years newer too!


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[BC250R]

All pivots in the 06 rear linkage and shock run needle roller bearings as oppose to the rubber mounted steel bushes in the 85/86.


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[BC250R]

Originally i was intending to only run the 06 swingarm and keep the original 86 shock with a combination of both for the linkages. This conversion was done on an 86 TRX in the states and was pretty straight forward. As you can see here on the ATC, this is the best combo i found with the 86 shock and its still jacked up way too much. It would have handled like crap not to mention how lame it would have looked. The full 06 rear was the answer, though the rear most link still had to be lengthened 45mm to achieve the ride height i was after.


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[BC250R]

OK, this is how its done. First we get the swinger bolted in the frame.
The inner pivot bearing tubes are the same ID as the 250R so the same swinger bolt can be used.
The width of the 450R swinger is almost exactly the same as the 250R so nothin to do here!
The distance between the 2 inner pivot bearing tubes is to narrow to accept the rear engine mount so they need to be shortened a touch. (Thanks Ash for doing this for me). I've read that you could use the 250R inner tube in the 450R bearing but i cant confirm this.



The shorter one is the original 250R. The other is the shortened 450R. The 450R swinger runs a seal inside the swinger end so shortening the tube does not affect this.






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[BC250R]

Next step is to get the front linkage to bolt into the frame. Once this is in, the rest of the linkage simply fits together as it would in the 450R.
TIP make sure you get all the hardware with the linkages. ie the bolts and bushes, Especially the rear most bolt that attaches the link to the swing arm as it is just plain weird!

As you can see here, the link hits the gusset on the frame. This has to be trimed to allow the link to move freely, especially once the rear link is lengthened to drop the ride height.



This shot shows the area coloured in blue removed and the travel now uninterupted. (sorry about the blury pic)



As you can see here, the bush for the link has a 10mm ID. The bolt shown is the standard 250R, it has a 12mm OD. The bush furthest to the right has been made (Thanks Ash! again) to have the same OD as the 450R bush with the 250R ID to accept the 250R bolt.
TIP It was easier to spin up the new bush than drill out the original 450R bush. This is becuase Honda has done such a good job on the hardening. It could be drilled with the right (expensive) drill bits.



Here is the new bush with some spacers i roughed up to keep the link centered. This is needed as the new link is about half the width of the original. I would like to make a new inner bush that runs the full length of the frame socket (about 72mm) and then spin up the spacers to fit over this. I found my roughed up bushes difficult to assemble in the frame. This new idea means you could assemble it out of the frame and simply push the bolt through when positioned.



At this stage the whole swinger and link system is in. You could attach the shock at this point but the ride height is very wrong. I found this after fitting the shock. A mod to the linkages was made to fix this so i'll talk about this now.

This pic shows the linkage set. (shown with a 250R shock) The way the pic is taken, the frame would be to the right, wheels to the left.
(Dont let the shock angle fool you, i didnt know this myself when i took the photo)

By lengthening the rear linkage (left), it pushes the centre join of the linkages, and there fore the lower shock mount, down. This happens as both of the other ends are fixed. By lowering the bottom of the shock, this brings the frame (ride height) down.



To see how much longer this needed to be i put a trolley jack under the frame and took the weight of the suspension first. Then i removed the bolt joining front and rear linkages. Once this was done i then let the jack down until the bike sat at the desired height. I then measure the distance the linkage join bolt holes were from each other. In my case it was 45mm to achieve my original ride height. (Before removing the 250R swing arm and shock, i measured the distance from the seat latch area to the top of the bearing carrier)

To lengthen the linkage i (read Ash! thanks) cut the linkage in two then ground the pieces to fit inside a length of alloy square tube. Slid the two pieces until it was the correct length, then welded the tube to the linkage pieces. ( this photo shows an adjustable version cause Ash didnt trust my measuring capabilities )


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[BC250R]

Now for all the people who have asked about keeping the original shock, i have since thought long and hard about it and it can be done easily.

Go back to the last step and just make the link longer by more than the 45mm and it should work. To attach the shock you should be able to just pack the gap between the lower shock mount and the linkage. I dont think this is much though. From memory i believe the bolt is the same size as the inner bush ID on the link so there is nothing to mod.

ADVANTAGES AND DISADVANTAGES OF USING THE 250R SHOCK
Dont have to cut or hit anymore of your shinny frame.
Dont get to use cool machines like angle grinder and hammers.
Heaps quicker conversion
Have to do other jobs around the house
You lose the superior workings of the 30 year newer 450R shock. The needle roller bushes alone make it super smooth. The bump and rebound adjustments are really easy to get to and they work.
You wont have the reserviour fixed at the top of your shock meaning you lose your airbox (i dont run one anyway), have to move your whole exhaust by making and moding all mounts and have to dimple (read hit with hammer a lot)your frame for clearance.

My goal from the start was to improve the handling performance of my bike. With that in mind i had no hesitation on making the mods to get the shock to fit as i do not think you will get a worthwhile result (other than looks) keeping the 250R shock.

That said, this could be done as a two staged mod to appreciate each step.

Ideally i would have copious amounts of money and do stage one only and fit an Elka or Ohlins aftermarket shock that has a remote reserviour.
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[BC250R]

Nice work Tony.
Is the adjustable link all the way out? Mine is still abit lower than that so i was wondering if yours get down a bit further.
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[stitch250R]

cripes!
that was quick. how good do they look.. nice job

[BC250R]

Before I post up the rest of the conversion up I'd like to say a huge thanks to:
Scott Bently for providing me with all the 450R parts at prices to rival US ebay. He had all the bits in stock and all were in excellent condition.
Ash for doing the machining jobs as well as extending the linkage.
And Stitch for helping me with links early in the piece.
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[BC250R]

Looks good T. You will have to bring the chain gaurd out to the frame or it wont be under the chain. Just pack the 2 mounting bolts about 5mm. the you may have to trim the front inner radius to get over the cap. Then unfortunately you will have to grind a "profanity removed" load out of the front to clear the front sproket. Shame to do all that to a shinny new bit. Oh well it only take one ride to take the shine off anyway.
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[ashnery]

That is awsome work boys ..and thanks for sharing it with the rest of us..
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OH "profanity removed" I SAID "profanity removed".......OH "profanity removed" I SAID "profanity removed"

[PC]

I rode Bretts Trike today with this conversion and I have never felt a better handling Trike.
With this new plush rear end it actually makes the front end work better with both front and back being surprisingly balanced.
I found myself hitting some pretty big holes and instead of rebounding back and nearly bucking me off this thing just ate it up as if nothing was there.
The 3.2kg weight difference felt more like 10-15 kg when you were throwing it around.
This is what the ATC 250r would feel like if they still made them today.

Well done Brett...........I'm starting mine tomorrow.

[stitch250R]

PC wrote:

I rode Bretts Trike today with this conversion and I have never felt a better handling Trike. With this new plush rear end it actually makes the front end work better with both front and back being surprisingly balanced. I found myself hitting some pretty big holes and instead of rebounding back and nearly bucking me off this thing just ate it up as if nothing was there. The 3.2kg weight difference felt more like 10-15 kg when you were throwing it around. This is what the ATC 250r would feel like if they still made them today. Well done Brett...........I'm starting mine tomorrow.

was hoping this was the case. 450r shock it is then!

[stitch250R]

Here is the new bush with some spacers i roughed up to keep the link centered. This is needed as the new link is about half the width of the original. I would like to make a new inner bush that runs the full length of the frame socket (about 72mm) and then spin up the spacers to fit over this. I found my roughed up bushes difficult to assemble in the frame. This new idea means you could assemble it out of the frame and simply push the bolt through when positioned.





[/quote]

wondering if anyone can get the exact measurements to make this full length bushing described above?

[PC]

stitch250R wrote:

PC wrote: I rode Bretts Trike today with this conversion and I have never felt a better handling Trike. With this new plush rear end it actually makes the front end work better with both front and back being surprisingly balanced. I found myself hitting some pretty big holes and instead of rebounding back and nearly bucking me off this thing just ate it up as if nothing was there. The 3.2kg weight difference felt more like 10-15 kg when you were throwing it around. This is what the ATC 250r would feel like if they still made them today. Well done Brett...........I'm starting mine tomorrow. was hoping this was the case. 450r shock it is then!

I don't think you would get the same result with the original shock, The 450 shock is what makes this work so well.

[stitch250R]

yeah mate i have the 450r shock on the way

[BC250R]

PC wrote:

I rode Bretts Trike today with this conversion and I have never felt a better handling Trike. With this new plush rear end it actually makes the front end work better with both front and back being surprisingly balanced. I found myself hitting some pretty big holes and instead of rebounding back and nearly bucking me off this thing just ate it up as if nothing was there. The 3.2kg weight difference felt more like 10-15 kg when you were throwing it around. This is what the ATC 250r would feel like if they still made them today. Well done Brett...........I'm starting mine tomorrow.

WOOOOOOOOO HOOOOOOOOOOOOOO
OH YEAH OH YEAH OH YEAH!!!!!!!!!!!!!!!!!

Cant believe how good this turned out. I could see the bumps, i felt the front hit the bumps, was waiting for the back to hit the bumps, but it just didnt happen!

SUPER SUPER PLUSH.
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[BC250R]

stitch250R wrote:

Here is the new bush with some spacers i roughed up to keep the link centered. This is needed as the new link is about half the width of the original. I would like to make a new inner bush that runs the full length of the frame socket (about 72mm) and then spin up the spacers to fit over this. I found my roughed up bushes difficult to assemble in the frame. This new idea means you could assemble it out of the frame and simply push the bolt through when positioned.

wondering if anyone can get the exact measurements to make this full length bushing described above?[/quote]


Front linkage bush (shown)

New inner bush to be 72mm long x 12mm ID x 16.5mm OD(or bloody close to but have originals to measure off)

2x outer bushes for centering will be 20mm long x 16.5mm ID x 25~30mm OD.

Top shock bush

New inner bush to be 50mm long x 10mm ID x 16.5mm OD (see above)

2x outer bushes for centering will be 10mm long x 16.5mm ID x 25~30mm OD.

I talked to Ash about spinning these up last night. He said if I'm looking at multiples he could set up the big machine on auto to spit out a few duplicates. If anyone is interested let me know SOON.
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[stitch250R]

put me down if he can do it..
id say Aussie would be keen too

[BC250R]

I was just looking at 07 400EX rear shocks on ebay. They look very similar to the 450R but the reservior is centred. This would eliminate having to mod the frame, though it may get in the way of the intake. Has anyone got one for a closer look?
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[Devil250R]

Do you have an exact length the inner pivot bearing tubes from the 450R need to be cut to in order to fit, along with the 250R rear motor mount? Thanks.