Confirmation on front master cylinder problems... - Honda ATV Forum
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post #1 of 8 (permalink) Old 06-28-2019, 01:25 PM Thread Starter
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Confirmation on front master cylinder problems...

1988 TRX300FW, here's what it's doing.

When I first got it, the front brakes just really sucked. They would work weakly, but not where I thought they should be. So I cracked open the master cylinder and what I found was fluid that was as black as night. I sucked out the oil fluid and refilled with new. Worked the handle till it turned black again, rinse, repeat. Kept doing that till it stopped turning black. Then I bled the brakes, starting with the front left.

Once I changed the fluid, I got some new problems. Now if you hold them down, it will go solid at about 2/3 pull, then slowly sink to the handle after being solid for about 3-5 seconds. If your on a hill, you can stop it with the fronts fine, but once the handle starts sinking it will start rolling again. And lastly, after about 2-3 good uses, you have to give it 30 seconds to recover or it just sinks right to the handle without really doing much of anything. They will come back, but it's the same dance once they are back again.

I think the master cylinder is shot. It's allowing leak by. I'm thinking at this point of buying an aftermarket unit, and also a rebuild kit. I'll put the aftermarket unit on, and rebuild the stock unit in my spare time. I don't really expect an aftermarket unit to last like the stock one did, so once it starts failing I'll put my rebuilt stock unit back on. I'm thinking of doing it that way because I've ran into situations on older bikes where the stock MC units were just too worn to take a rebuild kit and work right. But it caused me to chase my tail for 6 months. An aftermarket should work out of the box for at least awhile, and that will 100% verify it's the MC. That way I won't be chasing gooses if the stock unit is just too worn internally.

Any thoughts?

And on these 4x4 models how the heck do you adjust the front brakes? Moving one wheel moves all four, and there is enough resistance trying to move the whole drive train how do you tell when they are "just engaged enough to drag". There is ALWAYS drag due to the drivetrain....?

1988 TRX300FW Fourtrax
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post #2 of 8 (permalink) Old 06-28-2019, 03:03 PM
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Pinch the rubber brake hose right at the master cylinder with a pair of pinch pliers or a vise grip and a piece of card board or rubber so as to not damage the hose , with the hose pinched you should get a hard lever and not be able to get the lever to touch the bar and it hold and not bleed down , if that happens then the master is good , and the problem is brake adjustment , worn out shoes and or drum or air in the system ----------if it passes the test above them while you have pressure on the lever with the line pinched , release the pliers and hold the lever down , after the surge of fluid goes thru , put the pliers back on , pump it again and do the same thing , after about 5 times of doing that , then put pliers of the rubber hose at the tee to one side of the brakes , so you are only sending fluid to one side , do the pump , pinch , release thing again while opening the bleeder screw , move the pinch pliers to the other side and do the pinch bleed thing again
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post #3 of 8 (permalink) Old 06-29-2019, 12:19 AM Thread Starter
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Quote:
Originally Posted by fishfiles View Post
Pinch the rubber brake hose right at the master cylinder with a pair of pinch pliers or a vise grip and a piece of card board or rubber so as to not damage the hose , with the hose pinched you should get a hard lever and not be able to get the lever to touch the bar and it hold and not bleed down , if that happens then the master is good , and the problem is brake adjustment , worn out shoes and or drum or air in the system ----------if it passes the test above them while you have pressure on the lever with the line pinched , release the pliers and hold the lever down , after the surge of fluid goes thru , put the pliers back on , pump it again and do the same thing , after about 5 times of doing that , then put pliers of the rubber hose at the tee to one side of the brakes , so you are only sending fluid to one side , do the pump , pinch , release thing again while opening the bleeder screw , move the pinch pliers to the other side and do the pinch bleed thing again
I had read about that process, but hadn't tried it yet. With 31 year old hoses I was kinda leery about clamping on them. I might pick up some hose clamp pliers tho and give it a try. They would be useful tools to have either way.

Thanks for the reply!

1988 TRX300FW Fourtrax
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post #4 of 8 (permalink) Old 06-29-2019, 01:08 PM
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Rebuild the MC. Why buy another? Rebuild for a Honda kit is $30-40. That's with the black round piece inside the MC. Mine didn't need that but I got it anyways. It was $6. In my case (96 300) I probably could have just cleaned it and it worked. Yours is much older and might need the seals.

I put my adjusters all the way in, then adjusted them out equally until I felt them dragging on the drum. With all 4 wheels in the air you'll feel it. Then I backed them off 3 clicks. I read to do it that way on this site.

Someone else here mentioned a MC from a different Honda model is much cheaper than a MC for a 300. They'll probably chime in.
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post #5 of 8 (permalink) Old 06-29-2019, 08:38 PM
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got a master cylinder kit for the 2000es 450 for $20, Honda East, Toledo. OEM

clymers manual,service manual..
"what a good giff, the good lord gee us,not to see ourselves,as others see us"
hard to talk to morons. even more so, when related..
"ya should get 3 people ta smile or laugh every day" all will feel better
"sometimes, when drinking 5 or 6 bud's, nipping JB, Jim Beam, cinnamon in between, i start thinking sideways,,i have too though, ta match the way i walk" ed
"those that dont study history, are doomed to repeat it"
"I HOPE i aint wrote nutting else stupid" "funniest comedy dont need curse words" "teach how to think, not what to" ed
"Genius can be measured,not stupid" Albert Einstein
"when you get to old to learn, then what good are you" ed
i havent done friends list,if i do, R the rest not friends?
2000 450es TRX
2 grass hog 4x4s
sum humor adds up
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post #6 of 8 (permalink) Old 07-01-2019, 02:20 AM Thread Starter
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Quote:
Originally Posted by Budweiser View Post
Rebuild the MC. Why buy another? Rebuild for a Honda kit is $30-40. That's with the black round piece inside the MC. Mine didn't need that but I got it anyways. It was $6. In my case (96 300) I probably could have just cleaned it and it worked. Yours is much older and might need the seals.

I put my adjusters all the way in, then adjusted them out equally until I felt them dragging on the drum. With all 4 wheels in the air you'll feel it. Then I backed them off 3 clicks. I read to do it that way on this site.

Someone else here mentioned a MC from a different Honda model is much cheaper than a MC for a 300. They'll probably chime in.
I've had problems with the piston being worn on 80's bikes far to many times to trust a simple rebuild kit to be a reliable fix. I like to get decent yet cheap chinese MC's as a "benchmark". I've found normally they work out of the box, and even sometimes last a few years. Once I verify it is in fact the MC, I then work on rebuilding and testing the rebuild on the original one. Might sound convoluted, but I've wasted more months of my life running down brake problems that were caused by a faulty rebuilt MC that I don't feel confident in rebuilt units. (I've also had bad luck with rebuild kits being crap)

However, that's neither here nor there. I'm still going to try all the other suggestions before writing this MC off. And only if everything else checks out will I swap the MC's. (I've already ordered the new one, but I think it will be here before my boss returns from Colorado with my bike!! LOL)

I NEVER have a problem having spare parts sitting on the shelf! I can't even begin to count the times it's saved me in a pinch!

I'll report back with my findings once my bike makes it back from it's little trip without me. Told the Boss if he breaks it he buys it, so maybe I'll get a new ATV out of the deal?? LOL.

1988 TRX300FW Fourtrax
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post #7 of 8 (permalink) Old 07-01-2019, 04:35 AM
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Quote:
Originally Posted by Budweiser View Post
Someone else here mentioned a MC from a different Honda model is much cheaper than a MC for a 300. They'll probably chime in.
Almost any Honda M/C will fit , my 300s mostly have the TRX250 or ATC250 M/C on them , I like them as they have a larger reservoir and I had a bunch of them laying around ---- my 450 has a Yamaha Grizzly 700 M/C on it
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post #8 of 8 (permalink) Old 07-01-2019, 09:41 PM
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Power Sports Dealer, has taken over the market, or some derivative thereof. so, no much, no matter, where ya go, ya aint getting the discount, that ya once was.
i just got a kit for mine, #11, #6 maybe, if it has the gasket, that stops the air from getting through at the top of the cylinder. #18, the top screws that hold the the top cover down.
A master cylinder is a Master cylinder, no matter what atv it come off from,, no air inside of it, no air in the lines, no crud in either one, including the slave cylinders, no crud... cant say much more.

clymers manual,service manual..
"what a good giff, the good lord gee us,not to see ourselves,as others see us"
hard to talk to morons. even more so, when related..
"ya should get 3 people ta smile or laugh every day" all will feel better
"sometimes, when drinking 5 or 6 bud's, nipping JB, Jim Beam, cinnamon in between, i start thinking sideways,,i have too though, ta match the way i walk" ed
"those that dont study history, are doomed to repeat it"
"I HOPE i aint wrote nutting else stupid" "funniest comedy dont need curse words" "teach how to think, not what to" ed
"Genius can be measured,not stupid" Albert Einstein
"when you get to old to learn, then what good are you" ed
i havent done friends list,if i do, R the rest not friends?
2000 450es TRX
2 grass hog 4x4s
sum humor adds up

Last edited by LedFTed; 07-01-2019 at 09:45 PM.
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