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In my attempts to get rid of this whale dick air cleaner on my FXR, I've run into a lot of confusion on compatible backing plates for early 90s evos. Trying to find my original plate #29134-90 seems to be a lost cause but other mid to late 90s plates seem to pop up regularly on ebay. I've got an original Low Rider Convertible round cover on the way and want to keep a somewhat stock look. Since I'm running a Mikuni carb are other years backing plates usable? Should I go with an SE backing plate?
Other than the case breather attachment nipple @ the 7 o'clock position and lawn mower looking air filter in the earliest ones, the only difference is the mounting hole diameter for the heads. The '93 up are top breathers and you can use those backing plates successfully with the original 5/15" bolts on a pre- '93 Evo. They're all over fleabay, just look carefully, many are for the butterfly. (different bolt pattern)
At the same time, this adapter looks like it might accommodate either, I never used one, so can't say for certain. And yours is an S&S engine so I have no idea what the heads look like where the backing plate bolts.
You need to search - Mikuni HSR 42mm 45mm Air Cleaner Adapter CV Style Air Cleaners
Thanks, I saw that and plan on picking that up regardless of what route I go. My main concern was if the plastic backing plate was molded to conform around the oem carb and would interfere with the mikuni carb or if there were other things to look out for with the AC baffles or depth of the head mounting holes. If I remember correctly, there was an HD thread adapter that would convert the larger holes for the smaller head breather style. But I have noticed that the S&S heads I've got have something that's not just a standard bolt and reminds me of a banjo bolt style so I might just have the correct pattern for the newer top breather AC plates. I'll post more detailed info on what I've got tonight.
Thanks, I saw that and plan on picking that up regardless of what route I go. My main concern was if the plastic backing plate was molded to conform around the oem carb and would interfere with the mikuni carb or if there were other things to look out for with the AC baffles or depth of the head mounting holes. If I remember correctly, there was an HD thread adapter that would convert the larger holes for the smaller head breather style. But I have noticed that the S&S heads I've got have something that's not just a standard bolt and reminds me of a banjo bolt style so I might just have the correct pattern for the newer top breather AC plates. I'll post more detailed info on what I've got tonight.
That's an excellent question. The CV has the large slide diaphragm chamber at the top which the Mukuni does not. So it's possible the earlier butterfly backing plate would work if the adapter ring has the correct bolt pattern. But it sounds like you have a top breather engine already which would require the post - '92 (CV) back plate.
I'm strictly a CV guy but maybe some of the others with more hands on will wander by before you need to pull the trigger on the backing plate. Otherwise, I can help with OEM numbers for the air filter, breather tubes, etc. when you get close.
Thanks for the info, I figured it would be best to go with a screamin eagle setup that uses the stock cover and that seems to be the only route I can go at this point.
If you do your homework you can find the backing plate cheap, fit early years of a Twin Cam also. Found a backing plate nobody bid on Ebay and got it for like $2.60.
If you do your homework you can find the backing plate cheap, fit early years of a Twin Cam also. Found a backing plate nobody bid on Ebay and got it for like $2.60.
I'm eyeing a stock plate for a 86 and another for a 92, leaning towards the later . Also just ordered a parts and accessories catalog from 97 that will give me part numbers and more information on fitment with the screamin eagle stuff.
Well I was able to snag a backplate off a 94 Heritage for cheap and mounted it up just to see if there were any clearance issues and its seems to work with minor interference. Since this post, I've received a 97 and 03 P&A catalogs to go over part numbers, and I've discovered I've got the Screamin Eagle flavor of Mikuni's HSR 42 carb. I bought the adapter plate mentioned above and test fitted everything including a K&N filter and so far everything works but a fair amount of coercion is needed to get things to fit together, especially at the head bolts which I still need to find a bolt that will let me get a socket in there to tighten it down, might see if I can find the period correct breather bolts. There's also a gap between the cover and backplate when the filter is installed so I'm sure that I also need the gasket that goes around the cover to help seal.
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90s AC back plate compatibility
