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Discussion Starter · #1 · (Edited)
I've got a mess here, folks. I'm helping a friend with his Brute. He put it away almost a year ago and bought a SXS because he has a knee that hurts too much to ride quads anymore.
But he wants to get it going again now because he's going in to get a new knee.
So he gets it out of the shed and says it wouldn't even make it to the end of the driveway without dying unless he left the choke on. And it is a bear to start, and it pops and backfires out the exhaust.
So I'm thinking valves need to be adjusted, old bad gas in carbs--they need a cleaning, fresh gas, tune up, right?
So I go over to do that stuff, and watch his wife pull the Brute out of the shed. It's putting out blue smoke pretty bad, and I ask him about it. He says the last time he rode it, he went about 100 miles, and it went through most of a quart if oil. Yikes.
So I get into the airbox, and it's got a good filter, oiled, and no dirt visible inside the carbs. But I go to take the airbox off and find that the two hose clamps in the picture are literally hanging off the boots. Not good. I'm not sure if it's as critical on these BF750's, but I know the intake boots on the Prairie's have got to be tight and sealed off or it's screwed.
Anyway, I get into the valves, and to my amazement, they are perfect! No adjustments required. So then he tells me that he brought it into a local shop here a couple years ago for a tune-up. They say they had to adjust the valves. It had less than 3500 miles on it at the time. It now has 4700. OK, this just keeps getting more interesting!馃お So obviously, they were the ones who forgot to tighten the hose clamps!
And I'm wondering why did the valves need adjustment with that few miles anyway?
So, I pull the clutches, tighten the belt (it was quite loose), free up the weights, deglaze, etc, and put them back on.
So now I'm wanting to pull the plugs. I get them out and they are wet and black as licorice.
So I'm thinking at this point that there isn't anything wrong with the valves, the sputtering might just be the carbs need cleaned, but it could just be fouled plugs. So I put two new plugs in, put the airbox back on, and fire it up. It starts instantly, and runs without choke. I take it for a spin, and it seems to have full power, and runs pretty well, but still has the occasional sputter out the tailpipe. So I'm thinking the carbs might still need a cleaning, and maybe some adjustments. He says he thinks the original jets for sea level and everything are still in it, and it does smell rich.
So I leave the plastic off and tell him where to take it to have the carbs cleaned and adjusted because I don't have the stuff for the larger bf750 carbs.
Anyhow, I get thinking on the way home.......I'll bet that first shop dinged him for an unnecessary valve adjustment, then forgot to tighten up those hose clamps, then it ingested dirt, ruined his rings and/or cylinders, and now it fouls plugs so bad that it won't start, runs like crap, and goes through a ton of oil. He can get the carbs cleaned up, but it's still going to have issues running well unless he keeps putting in new plugs often.
I'd don't know. I'd be for doing a whole new top end in it, but that's up to him. I've done all I can do for now. But I think I'd be letting that shop know they may owe him a new top end for not getting those hose clamps tight around the intake boots, don't you think?
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Yeah with those box-side clamps loose it will let unfiltered air in and that's...well.. death to the rings...and usually valve seats and guides. It will need a full top end and a complete fuel system cleaning as well as a full professional carb cleaning.
 

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Discussion Starter · #3 · (Edited)
Yeah with those box-side clamps loose it will let unfiltered air in and that's...well.. death to the rings...and usually valve seats and guides. It will need a full top end and a complete fuel system cleaning as well as a full professional carb cleaning.
What a tragedy. Two screws "screwed" this machine. It's in great shape and has been treated well otherwise. Only 4700 miles too.

If we're going to pursue this with the shop that left them loose, I need to know more about that bottom of the airbox.
It does fit tight around those boots without the clamps being tightened. It's definitely a better design than the Prairie's. I can see why they went to this design for the future.
And the inside of the boots all the way down into the carbs looked clean. Could real fine dust still get by and get in there?
 

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What a tragedy. Two screws "screwed" this machine. It's in great shape and has been treated well otherwise. Only 4700 miles too.
There's just no excuse for this kind of stuff. Now if that airbox set just right, it might get away without the clamps but as anyone who has ever put a carbed Brutes air box back on will tell you...its a MF'r to get straight. Still..using that much oil tells the story well enough.
 

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Discussion Starter · #5 ·
There's just no excuse for this kind of stuff. Now if that airbox set just right, it might get away without the clamps but as anyone who has ever put a carbed Brutes air box back on will tell you...its a MF'r to get straight. Still..using that much oil tells the story well enough.
So I have a little tool made for windshield installers to help get moldings around the glass. It's kind of a tapered pick with a bend in it. I used it to get the boots up into the bottom of the airbox. Without that tool, I can see how it would drive someone mad to put the box on. But once the boots went through, everything lined up good. The two collared bolts that hold the airbox to the frame were lined up and went right in. And I think I remember seeing a notch and tab on the bottom of the box that was there to probably help align it. Is this unique?
 

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So I have a little tool made for windshield installers to help get moldings around the glass. It's kind of a tapered pick with a bend in it. I used it to get the boots up into the bottom of the airbox. Without that tool, I can see how it would drive someone mad to put the box on. But once the boots went through, everything lined up good. The two collared bolts that hold the airbox to the frame were lined up and went right in. And I think I remember seeing a notch and tab on the bottom of the box that was there to probably help align it. Is this unique?
Yep. And I have a tool like that too...lol I also used it on the belt cover exhaust boot.
 

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Discussion Starter · #7 ·
Yeah, it's a must own tool for working on Brutes. Lol.

So, high chance that those two clamps must be tight to keep all dust out of the carbs?
 

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The boots on the brutes do go on pretty snug, but any ingestion of dust is a killer to interior components, and there are quite a few very small orifices in those carbs that take literally nothing to clog up. If it was mine, I鈥檇 re and re the top ends and clean the carbs. The carbs are really not that complicated and the rebuild kits are pretty cheap. Same for the top ends. Hone the cylinders, slap on some new rings, freshly rebuilt carbs and new fluids all around and she鈥檒l be like new!
 

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That sucks, definitely sounds like she ingested some dust. Doesn't take much of a gap for the silty moon dust/talcum powder we have here in Utah to get into everything unfortunately. I would do a dry compression check and then a wet compression check. That should tell you everything you need to know. Hopefully its a reputable shop that will work with you and own up to their own mistakes but there are probably more crappy a-hole owned shops in the Wasatch Front than there are good ones.
 
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