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Fuel System: Gas (Petrol) tanks, Carburators
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Spargett Member
Posts: 592
Joined: Wed Jun 18, 2008 10:19 pm
Location: Los Angeles, CA

Post by Spargett » Fri Oct 01, 2010 4:00 pm

The model number for the K&N Filters Vince used are RU-0210. You can order them directly from K&N with free shipping if interested. Here they are with the covers off. I will fabricate a mount soon, but for now they're sturdy with hose clamps and fit under the covers just fine.


Vince Lupo Member
Posts: 1371
Joined: Wed May 04, 2005 7:17 am

Post by Vince Lupo » Fri Oct 01, 2010 4:44 pm

What I did was to get an old set of stock air filters and use their metal frames. Then, you weld a collar on the inside of them for the K&N filters to clamp onto. It's plenty sturdy that way.

56_oval Member
Posts: 277
Joined: Sun Oct 24, 2010 2:37 am
Location: Dallas, TX

Re: Filters

Post by 56_oval » Thu Dec 02, 2010 10:31 am

ggray wrote:Forgot to attach the photo............
Is that rear chrome bar stock for the scrambler? My CB came with one on it so I was curious...

marzini Member
Posts: 51
Joined: Thu Nov 08, 2007 3:54 pm
Location: Santa Fe, New Mexico

Post by marzini » Mon Jul 31, 2017 3:42 pm

Another K&N universal mount filter that could fit in the CB77's application is the K&N RU-0175 Universal Clamp-On Air Filter. ... od=RU-0175

Its molded ends (3" diameter front and rear) coincide with the location of the rubber bumpers that rest against the side-panels. If anything, the rubber bumpers/brackets would seem to hold the filter all the more securely where they touch the air-filter's end-rims. The RU-O175's inlet flange is 1.5" and the overall length of the filter body is 6". You might need to jet larger with that filter, especially if your exhaust is aftermarket.

My K&N filter is the RE-0240 which is slightly conical (3" front and 3.5" rear) and 3.5" overall length. I suspect that my relatively short unit is comparable to the breathability of the CB77 OEM unit. I use two hose-clamps and Napa PN# 3088 hoses with a 1.25" length of 1.5" exhaust pipe to join the the filter to the hose. You can't see the metal pipe inside the rubber hose and filter mounting flange. One of the hose clamps rests on the Honda's front air-housing bracket; there's no sagging.

I fit a short piece of slit rubber vacuum-tubing along the top of the front bracket to pad that hose-clamp.

At 6'300', I am basically running stock jetting (middle or 2nd notch from the top on the needle) with the RE-0240. It is conical (3.5" at the rear), so the filter is pinched securely at the rear-most dimension between the middle of the side-panel and the parallel inside metal-work that houses the battery.
'62 CB77, '76 XT500

marzini Member
Posts: 51
Joined: Thu Nov 08, 2007 3:54 pm
Location: Santa Fe, New Mexico

Post by marzini » Thu Aug 31, 2017 7:05 pm

I had K&N RU-0240 filters (3" x 3.5") and the engine felt a bit starved. I actually had to jet down one step to a 130 on my cb77 to get a good mixture and better response as well as noticeably higher revs winding out (it was just going flat at 8k rpm with the 135 jet + short K&N).

I put in a set of K&N RU-0175 (3" x 6") and was able to use the 135 jets. Now I'm feeling the engine running "looser" and definitely getting all the revs the engine wants to put out.

Size matters. The inlet size is 1.5". I think the radiator hose is NAPA PN3088. I have a short piece of 1.5" exhaust pipe to joint the k&n to the radiator hose.

Sorry, I was unable to show a picture cuz it said "security reasons".
'62 CB77, '76 XT500

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