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Post by skucera on Jul 30, 2012 1:32:11 GMT
I had time today to try to figure out why my air horns don't fit around the throats of my carbs. I pulled one out of my airbox and tried to fit it over a single carb, and it looked too small... way too small. All four air horns are the same size, but they seem too small for the holes in the air box that they fit through. Also, the clamps are too big for the air horns.
So, I measured them. The OD of the carb mouth is 52mm, but the ID of the air horns is 46-47mm (there is some deformation from someone trying to cram the hair horns over the carbs). Duh, no wonder they don't seem to fit.
Did someone fit carbs from a larger bike onto mine? (I can't find the specs on the stock carb size at the moment, but I bet I'll run across it right after I hit the "Post" button.) Or, did someone put the wrong size air horns in my otherwise stock airbox?
Time to go looking for K&N's, or for correctly sized air horns....
If you have any clues for me, please help this make sense.
Scott
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Post by fz750horse on Jul 30, 2012 12:27:38 GMT
This is really common Scott - the rubber shrinks like mad, the rubber horns pop off the carbs and it's very difficult to get them to fit back on. The usual solution is to heat the collar part of the stack in boiling water and then ram it back onto the carb. The stock steel bands don't hold them very securely - some people have found very thin jubilee clips to replace them and I've used cable ties with no problems. Gavin
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Post by fz750horse on Jul 30, 2012 12:31:42 GMT
I also meant to say that there's a lot of play between the horns and the airbox. I clagged mine up with silicone, fitted them to the airbox, then fitted the whole lot to the carbs and left it a couple of days to cure - only had to do it once
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Post by Graham on Jul 30, 2012 17:04:13 GMT
I will add to that & say I did the heating in boiling water thing & sealed the rubbers at the air box but I also took the small spacer off the screw of each clamp & ground about 2mm off one end. This meant I could do the clamps up a bit tighter.
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Post by skucera on Aug 1, 2012 4:06:20 GMT
Those are great ideas. Having shrunk 5-6 mm in diameter seems amazing, but I have seen several posts about shrunken air horns on this forum, but they made me think 1-2 mm was what they shrunk.
Just to cover my bets I've ordered some 52 mm pod filters to slip over each carb. At about $10 each, it's insurance in case I can't boil and stretch enough to make the air horns work. We'll see how that works out. I may have to crush the sides in a bit to make them fit close enough in pairs, since the two carbs on either side are pretty closely spaced.
Scott
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Post by Graham on Aug 1, 2012 9:43:21 GMT
I have a set of pod filters for the exact same reason! Would like to have mine running right with standard set up 1st before getting too involved with filters but they are there as a back up.
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Post by skucera on Aug 13, 2012 5:06:57 GMT
Actually, boiling water and thick gloves worked very nicely weekend before last. All four air horns slipped over their carbs. Thank you for the idea!
Too bad I didn't have time this weekend to get out to the garage and work on it any. With visitors the next couple of weekends, I probably won't have time to work on it for awhile. Maybe I'll sneak out there some evening after dinner if I don't have to work late.
Scott
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ipa
New Member
Posts: 15
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Post by ipa on Sept 5, 2012 18:57:19 GMT
I had that problem with mine. I could get them on, but after a while at least one would make its way loose and I'd be idling at 4k. Swapped out with the K&N RU-2754 and haven't had a problem since.
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Post by Crusty on Sept 5, 2012 21:04:18 GMT
You probably didn't leave them on long enough to cool and set the size. The clamps are a bit suspect as well,it's difficult to get them to hold tightly.
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