Find a pair of the alloy outer covers on 71 bikes. They do seal very well but hard to obtain a used pair now. You might find some in the USA at autojumbles but over here the prices are rising.
I did buy one of those plastic covers in 1979 after i broke an alloy one and no new alloy ones obtainable and i also found it not very good.

 

I still have all of my parts off my 71… not sure of condition but I can look if needed.

 

I had a similar problem on one side of my 73 Tiger 750. I couldn't get the cover to seal and tried sealant to help but to no avail.

Eventually I used a very hot hairdryer to soften the plastic whilst fitting the cover. With a bit of time and patience I eventually got the groove in the cover edge to fit over the air filter housing all the way round. I bolted it up and applied a bit more heat then left it to cool. It seems to have largely retained the fitted shape and is now much simpler to refit when required.

 

Hi Bob
I know you wish to keep the look of the original bike but as Rambo has said unless you can find the alloy outer covers then sealing the originals will test your patience,especially if like Rambo you don't plan to run the filters .These leaks may also be contributing to your previous issue making one cylinder run hotter than the other . Personally I ended up fitting the retro plastic panels and POD filters . My bike runs really well whilst also shedding a few pounds so win,win

 

Yes, if you cannot find alloy side covers, maybe fit retro covers and use decent filters. Keep lookiing for the alloy panels though

 

Here's an alloy set on eBay ....

116271066002

 

There are no alloy outer covers in that sale. They tend to be very scarce as they normally get crunched in a fall off. I have 4 covers in the garage, 3 left and 1 right but it has taken about 20 years to find those good ones. I keep a set painted so i can replace any that get petrol on the paintwork.

 

OOPs! You're right, Rambo! I don't know what I was thinking!

 

Here is one for the right side for a single carb...
285207723636
@bob_3020, Try giving Ed Zender at Morrie's Place in Ringwood Illinois a call, he might have a set...
I just finished a complete rebuild of a 77' TR7RV and gave up trying to configure a different air filter set up. There's just not enough room to work with. The OIF tube is too close.
But definitely, the metal covers will solve your issue, I found a set on eBay a few years ago for under 60 bucks....

 

TR6 covers are rarer than the T120 . As you know, the TR6 covers do not have large holes drilled for the two carb inlet rubbers.

 

i never knew the alloy covers on my 72 were rare. i took the whole airbox off years ago to fit larger carburetters.

 

several sets for sale pn ebay right now

Triumph 650 Sidecovers for sale | eBay

Get the best deals for Triumph 650 Sidecovers at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

 

Hi, I see the alloy air filter covers are getting pricey. At last swap meet year ago, I saw several air boxes, only one alloy side cover. I bought it. Was end of day & seller was packing up. Was really a Harley swap meet. I got air box casting & one cover for $12. We was mad, but not mad enough to pack it up again. I got lucky!
Just like the swap meet air boxes are much more common on eBay. Where did the covers go?
The alloy cover doesn't have groove. It is slightly larger & slightly tapered. So the ID of cover is interference over air box. With some small gaps. So you'll need to find a way to seal alloy cover also. Factory said use thick heavy grease.

One of the problems with the plastic covers is they were overtightened. You can see this & it crushed the filter itself. Of course owner was trying to get the front part to seal.

Here's what I did with my plastic cover. I got some sheet stainless from Ace Hardware. Cut & bent into hooks. Attached to cover with screws & nuts. Peened screw tip over nut so they cannot fall off & get sucked into motor. Bought springs from Ace & cut them to right length. I install springs with needle nose pilers. I got thin self stick weather strip from Ace as well. cut it narrower lengthwise & stuck int in groove. I had to reform the groove in a few areas. This has worked quite well for some years now. As I said prior the foam is good for at least 2 years.

I don't know if your filter covers can be saved. Personally I'd get alloy ones. Fit them with some sort of seal. Felt tape comes to mind. Glued on with yellow 3M adhesive. Since I had the spare air box it was easy to check the fit from the inside. Sealing the gaps on alloy cover is not so simple as putting foam tape in a groove.

My plan with the alloy ones is fill the louvers, add Filler fin to rear edge & cut the Bonnie area off & weld in aluminum sheet to make the streamlined.
Don

 

The alloy cover doesn't have groove. It is slightly larger & slightly tapered.

I'm not saying you're wrong, I just don't remember the covers I fitted a few years ago not having the groove. I also owned a 1971 T120R and don't remember those covers not having a groove to mate with the air box.... 🤷‍♂️

 

you can buy stick-on door weatherstrip at a hardware store. put it on the mating surface, then put washers on the central mounting bolt until the cover can be snugged down tightly against the washers without deforming the cover.

 

Hi Happyfeet, Thanks for pointing that out! Dementia must be kicking in. I pulled the cover from the shed. The cover isn't tapered it has a "shoulder" that seats on face of air box. In this particular case, the cover has about 1/16" rock on the air box using a flashlight I can see light coming around the corner of gap where it rocks.

Saying that I have no idea what year the box & cover is. I don't even know if they were off same bike. I could be there was an alloy cover that had the groove.

That brings up a new thought. You could use bluing or the like. Then sand air box to match cover lip. Then use thin self adhesive felt tape wrapped around edge of air box. This would probably give good seal & last a long time. But I'd have to look closer at the overlap of shoulder.

Triumph had a good concept with the air box, but didn't follow through with proper sealing.

Here's some photos.
Don

 

Two Service Bulletins from Triumph

K

 

I was at the Eurojumble Today and looked around for alloy covers. I found quite a lot including a box of brand new BSAS 71/72 ones in Bronze and green paint. The prices were around £35 each but some sellers were asking £65 for 2 covers and the 2 centre sections. I saw about 15 in total but mostly T120r type with the holes for the 2 carbs. There were some for the TR6.

 

How far is Eurojumble from po-dunk rural Arkansas? IMHO, British motorcycle parts are become rarer and rarer in backwoods America. There's no shortage of chopper/bobber crap however. I refuse to resort to Uni Pods. I am going to start looking for alloy covers though.

 

hit up the swap meets. people still think the OIF bikes are ugly stepsisters in lots of places, and bits are inexpensive.

or do what i did and use 1976 honda 360 sidecovers, which are a perfect fit and cost $20 a pair. they even have a cutout for the right side hinge. i have a spare set i bought just in case i buy another OIF.

 

Honda 360 side covers? I'm having a hard time visualizing how that would fit on a TR6. I've actually located a few left hand alloy covers on EBay. The search continues for the right side.

 

no recent puctures, sorry. im using large K&N filters atm, and so took them off. but i was planning on putting em back this weekend, so maybe i ll have some images.

its not a direct fit, and is peculiar to my condition. the zip ties hold the wiring. once mounted, these are seamless.

 

Its a long way from USA. Southampton in the UK. Its popular for the Europeans to come over on a ship as seen by a coach full arriving and i guess they will stay for the other sale at Beaulieu which is very near. There were a few European sellers but it must be expensive to bring a large van over here. Of course, if they buy parts in person, it avoids all the customs and taxes.
There are more containers of old parts coming here recently from the USA, mostly old rusty Japanese 2 strokes but British bikes are also being found.
One low cost bike was a 400 mile 2 year old Benelli 400 at £2000 and it looked brand new

 

So I think the 71 aloy covers for the BSA 650 fit triumph also. Is that true?

 

They are the same covers. The BSA frame and T 120 are the same apart from different lugs for mounting the engine.
2 types, one for twin carbs and one for single. Single carb has a central cut out in the inner boxes and no large holes in the outer.
twin carb has no hole in the inner boxes and large holes in the outer for the two rubber inlets to the carbs.
BSA was made in 71/72 then it all went bad

 

I'm fighting with this on my 1978 T140E. Did they ever fit correctly? The plastic outer covers fit reasonably well as long as I don't use filters, which is a problem.

Like @bob_3020, I live on a dirt road. Filters are necessary.

Bob

 

Earlier in this thread I posted a couple of Service Bulletins. Biggest problem I have had with the OIF airbox covers is the PO cranked the fasteners down to tight and distorted the covers.

I did replace the original air filter with a 71/72 open style

K

 

I was having the worst time attempting to position the filter elements and the outer covers. The filters always moved. Because mine have sheet metal in the center, I used nuts to hold the filters in place. Of course, that required trimming the center "post" on the outer covers by the thickness of the additional nut.

I think that the outer covers are now reasonably well-seated, though I'll probably use silicone sealant around the edges before I'm finished.

Bob

 

Hi, On my '73 Tiger which has plastic covers I ended up putting cut down foam door/window gasket material from hardware store in groove of cover. Then added 2 springs across the front of cover. I has worked pretty well. If/as needed you can apply thin foam to the air filter face as well. You need to replace the foam gaskets every 3-4 years.

The factory set up is rink a dink to say the least. The round original 1970 version will fit many bikes without modifications, Then install retro side covers. Of course that changes look of bike.

There is a principle of carbs, how the vent & air filters. Carbs that vent float bowl into atmosphere need air filter that basically doesn't change air flow as it gets dirty. The air filter was oil bath or wire/gauze. Paper air filters were introduced, which if high quality clean air better than oil bath or wire gauze. It was soon found with a paper air filter, as they get dirty the level in float bowl would change due to the pressure differential. They vented float bowl inside the clean air part of filter. You can see the vent tube in many older carbs. Sometimes just a hole though.

Paper elements can work in Triumphs, but wire/gauze in better choice as the wire gauze has very restriction as they get dirty.

Don't think all brands of filters are made the factory thickness. The thickness can vary almost 1/4"! How does that effect sealing. Of course something won't seal.

The filters in photo were obviously crushed. But were they too thick? Or was filter cover & housing too thin.

My observation is many covers on OIF bikes are overtightened. Why? Most often in an attempt to get cover to seal around edges. It is a very weak design.

The plastic covers on T140 are even worse in my observation. Have a huge tendency to warp also. Often if never overtightened to front will warp out & allow dirty air into filter housing. The inside of filter housing will have some oil & fuel deposits, but should NEVER be dusty or have dirt. That is a sign the cover is leaking. The plastic is extra flimsy, but we have to deal with what we can get.

A ring of clips or screws on the perimeter would be ideal. Factory didn't do that.

On my '73 which have never ever been overtightened the front warped out. I fabricated some tabs from stainless steel screwed to cover. I riveted screw over should nut come loose it can't fall off. The other screw hole is threaded into thick plastic with loctite. Should it fall out it will only leak air, not get sucking into carb.

Here's a few photos of my covers fitted on bike. The springs are strong enough to pull the warped cover tight. The heat of riding has allowed to the cover to bend tight to the air box. Springs all around would be ideal. But not very practical. Looks matter too. The springs in front don't look silly or out of place. Needle nose pliers unhooks the springs for servicing. A spring above carb & below carb. This will still work on Bonnies. Harder to hook on springs by far.

The '71 & 72 allow covers are a direct fit. Of course look very different. Alloy is much stiffer. But still would benefit from springs. The alloy can be exactly filed to fit the housing. You'll still need a seal of some sort. Thick grease from the bulletin doesn't cut it.
Don

 

Don:

I like the round air filters but my T140E has a parallel port head, and there isn't enough room for them.

Your spring solution looks good.

Bob

 

Hi Bob,

like the round air filters but my T140E has a parallel port head, and there isn't enough room for them.

@Rancidpegwoman Peg's earlier suggestion didn't help?

Regards,