Triumph Rat Motorcycle Forums banner

1 - 20 of 28 Posts

·
Registered
Joined
·
29 Posts
Discussion Starter #1
I'm working on a '99 Legend TT.
I'm pulling the carbs to clean them up and discovered the airbox (and filter) are trashed and the secondary airbox is in pretty bad shape, too.
I've never liked pods so I will be purchasing a new OEM airbox/filter assembly. However, I am considering opening the airbox up by basically just cutting off the very back end of both sides. I'd also be leaving the secondary airbox off. I didn't find any info on this specific mod. What are opinions on a jetting combo to go with?
Exhaust is stock.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #2 (Edited)
I discovered that have 110/40 jets on hand. I'll probably go with these for now. Based on some of the comments I've seen, that sounds like it may be a reasonable combo. I'd rather only do this once.
Any experience to the contrary out there (on the jet sizes)?
 

·
Registered
Joined
·
1,983 Posts
I have a '00 Legend. I have cut an oval opening on the right side of the airbox and left the other side stock. I have STOCK pipes so my jetting is a little smaller. I am using 125's in all cylinders. I experimented with the opening after installing the 125's. I found the one 2" hole punched with a hole cutter was not enough, so I drilled a second one underneath it and joined the two holes with a sabre saw. The oval opening is about 2" X 4 1/2". If you have a free flowing exhaust, you might go a little bigger on the jets. I ran this setup on a 125 mile run last week and was really happy with it. As they say "results may vary". ...J.D.
 

·
Registered
Joined
·
993 Posts
I've done the same thing to two of my bikes. I've kept the rear box on since it had the seat lock and mounting point for the side cover.

The air box is going to have the back cut out, here is the cut line I laid out. I'm keeping the secondary box to retain the sidecover and I wanted the airbox opening to be as big as possible.





More to come tomorrow!
How it looks installed on the bike.

Had some time on the garage today. I installed the rebuilt and re-jetted carbs and the back-halfed airbox. I balanced them using the Morgan Carbtune tool which is awesome and easy to read.




As for jetting I'm at high elevation. I have 40 pilots and 135 mains on one bike with stock, drill out exhaust and the other bike has 40 and 132 with 3 into 2 header.

You being basically sea level I'd start with a 42 pilot and 145 main and take it from there. With the airbox cut open, installing and removing the carbs is pretty easy, disconct the throttle cable from the grip end.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #6 (Edited)
Thanks. Those comments definitely help. Those seem like big jumps for just opening up the airbox a bit BUT that stock opening does seem really small and restrictive so I guess it's not that surprising.
 

·
Premium Member
Joined
·
261 Posts
Rollins is right. My airbox is cut almost exactly like his in the pics and I am running 145 and 42's. I also put in Thruxton needles with no shims but may add a 0.5mm.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
1,983 Posts
The point of elevation is hardly ever mentioned in these discussions. It is a valid consideration though. I tune for 3000', the elevation at my shop, but when I ride it varies from around 2000-4000' most of the time. My bikes do not run well above 5000' I also think what the factory had in mind when they restricted the airbox opening so much was noise dampening, but restricting the airbox means restricting the jets....J.D.
 

·
Premium Member
Joined
·
261 Posts
Rollins is right. My airbox is cut almost exactly like his in the pics and I am running 145 and 42's. I also put in Thruxton needles with no shims but may add a 0.5mm.


Sent from my iPhone using Tapatalk


I said 145's, I went with 140's. 145's may be better..


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
29 Posts
Discussion Starter #11
Great info. 110s obviously won't work, then. You've saved me at least one carb rack pull.
I think I'll go on the conservative side (135/40) for starters since I'll be running the OEM filter element and my exhaust is unmodified.
I think I'll go ahead and order 140s, 145s, and 42s, just in case it needs more. If not, I should be able to use those in my TBS w/TORS when I start to monkey with the intake on that.
I'll report back on how it works out.
 

·
Registered
Joined
·
1,983 Posts
It would be interesting to take an old rear half of the airbox and some sheet plastic and make up something. All the used one I have had were already too hacked up the be useful. Anybody have a complete rear half they want to part with ? I'm thinking I could make a mock-up and run it through a laser printer. ...J.D.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #13
Wanted to report back.
Just to summarize... 1999 Legend TT, new OEM air box with back ends trimmed off of both sides, deleted secondary inlet box, stock exhaust, "sea level".
Put in 130 mains and 40 pilots with 2 turns out on the screws.
Since I deleted the secondary box, I re-hung the left side cover using rubber cushioned loop hose clamps.
The bike now has great snap off idle and pulls hard with a most satisfying intake roar. I'm calling it good for now.
 

Attachments

·
Registered
Joined
·
69 Posts
Old thread but not dead ;)

Anyway, did the airbox mod this weekend, opening it completely like Rollinslow84.
I have some questions for the people who has done this mod:

1. Did you buy a separate crank case breather filter or kept the stock through the airbox? Seems like there is a risk that water will get in to the airbox easier when its open like this, right?

2. I left out the silicone that seals the two parts of the airbox together, seems like that is not needed now as the only restriction is the filter now, right? Or am I thinking of this wrong?

Cheers!
 

·
Registered
Joined
·
69 Posts
This is what I did:




This is the separator I used. I had to flip the auto drain valve upside down so it would stay shut and not auto drain.
Looks pro :)

Maybe I'll try something similar but only if needed, you have pods so it is a little bit different.

Here are the plugs btw (I know they should be tested at a specific throttle position but with my jetted Mikunis they were black every time I looked), one taken with flash and one without, makes quite a difference in color. I would say they are closest to tan, maybe a bit lean but it's cold outside, around 5°C (40°F) so probably makes sense?

716501
716502
 

·
Registered
Joined
·
69 Posts
Maybe it's the photo, but they look pretty black to me...hm
There's hundreds of plug color charts on the internet. Here's a simple one that looks pretty good:

Still some around the edges but the electrode is not black anymore, maybe because it's the same plugs that previuosly looked exactly like the carbon fouled ones in the pic you uploaded? I replaced them with new ones now anyway so we will see next time I pull them :)

Nice bike collection btw! Trying to build something similar, have a 2002 HD Fatboy as my cruiser and would like to add a 60s/70s Triumph/BSA to rebuild!
 
1 - 20 of 28 Posts
Top