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Discussion Starter · #1 ·
I am trying to spec up a brake master cylinder repair kit having used a Honda trx 450 unit on a enduro brake upgrade. The first bronco kit I purchase the plunger was too large. The dimension of the plunger in my master cylinder is 51.4mm in length and 12.6mm in diameter at its widest. I can provide more info on the dimensions if it helps.
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I am trying to spec up a brake master cylinder repair kit having used a Honda trx 450 unit
I guess I'm just dense, but what's wrong with getting a TRX450 master cylinder kit?

No the dimensions do not help - just get the parts for the cylinder you used.

Question: how is using a TRX450 master cylinder an 'upgrade'?
 

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Discussion Starter · #3 ·
Hi,
As the TRX master cylinder is driving two brake callipers its a handy upgrade for a single calliper endure bike. My 04 WR450F has the crappiest brakes so I purchased what I am told is a 04/05 Honda TRX 450 master cylinder to boost the stopping power (this is after overhauling the original WR system, new hoses, pads, larger disc, master cylinder kit, bleeding...I tried everything to boost power to safe road riding levels). I bought a rebuild kit for the TRX 450 part but the kit parts are not the correct size (the kit could be wrong of course but I've checked the serial numbers of the Bronco kit) which makes me think there may be different version of the TRX master cylinder depending on the model variant e.g TRX 450R may be different to other models (cc or variant). I was wondering if anyone new from the measurements of the plunger, which master cylinder it was from and I could then get the correct kit to match. I appreciate its a tricky one.



I guess I'm just dense, but what's wrong with getting a TRX450 master cylinder kit?

No the dimensions do not help - just get the parts for the cylinder you used.

Question: how is using a TRX450 master cylinder an 'upgrade'?
 

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There were two different master cylinders for the front brake of a TRX450

98-04 TRX450S and ES used a cylinder that required kit 45530-HM5-630 which supersedes to 45530-HC5-006
04-13 TRX450R & ER used a cylinder that called for kit 45530-HA8-771

I could not find the dimension's to the cylinders in any of the service literature, but there were two different master cylinders used on 450's - you just need to get the kit for the one you have.

The same cylinders were used on 250's, 300's, 400's, 500's 700's and other models

I understand your thinking (2 vs 1), but it's faulty logic: With 2 calipers stopping wheels of smaller diameters even though the machine is heavier, the master cylinder of the quad probably has a larger bore and displaces more fluid, but it does so at a lower pressure. Hydraulic physics 101; larger surface area displaces more fluid at a lower output pressure for a given input pressure than a smaller bore displacing less fluid at a higher output pressure for the same input pressure. So going to a 4 wheeler master cylinder is actually a downgrade, but there are other factors to take into consideration; A 21 inch wheel has a greater mechanical advantage than the average ATV wheel, the size of the lines, the material the lines are made of, the length of the lines, the length of the lever operating the master cylinder and even the distance of the pivot point of the lever in relation to the point the lever make contact with the MC plunger.

Therefore a master cylinder with a larger bore that moves a higher volume of fluid will have a lower pressure on the caliper piston for the same given lever pressure applied.

Honda has a patent on the routing of the front brake line as it is part of the reason Honda has better brakes than the competition

Best way to improve your brakes is to switch the forks, wheel and brake from a Honda CRF450X onto your WR
 
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