Triumphrat

DrMath · 10-23-2005, 12:12 PM

I rejetted by bike about six months ago. I live in Annapolis MD 500 ft above sea level. I rejetted to 115 main 42 pilot 2 1/2 turns suggested by Brent at NewBonneville. Also removed the AI.

Since then my gas mileage BITES 30/35 city/highway. Also it seems I have a flat spot in the mid range (4000-5000 rpm) when accelerating. I ride aggressively (like to accelerate) but nothing insane, but even on long highway trips where I'm just cruising I average 33-35 mpg.

I checked the plugs and they are clean with a little lite orange on the post. Also checked for a loose vacuum plug. Did find the forward clamp on the large black rubber tube connecting the carb to the engine manifold needed alittle tightening. There was alittle carbon suet on the carb with the loose clamp. (Was that blow back from the carb).

Could that have caused the problem? If not any suggestion on how to tweak the mpg and eliminate the flat spot in the mid range.

dazco · 10-23-2005, 04:28 PM

Don't know about the MPG, but the main fix i see for the midrange all the time is to install TBS (thunderbird sport) needles or thruxton needles. In fact i have a pair of TBS needles in the mail now. Lots of rave reports on how well they fix that flat mid spot and even boost it a good bit. TBS needles seem to be the best route, as the thrux needles have been reported to be too rich in many cases. Plus it's said the TBS needles have the same taper as the thrux but a bit longer, so if you add a couple .5 mm shims it should approximate the thrux needles if you want. Go to bonnevilleamerica.com forums and do a search for TBS needles and you'll find lots of threads about people who've done this with very very few negitive reports. Search here too, tho the BA forum has more threads on them even tho they're concerning the america and speedmaster since thats who that forum is for. But bonneville owners can benefit too from what i've seen.

1409 · 10-23-2005, 04:33 PM

DrMath, how many miles do you have on the bike?

04BB..

badrufus · 10-23-2005, 04:53 PM

Hey Doc,
We're riding the same bike, 2005 T100, although I'm at 1800 ft. I have the Norman Hyde Classics, similar to the Togas, and have rejetted to 120 mains, stayed with 40 pilots, installed a K&N replacement filter with no airbox mods, and have one 0.5mm shim on each needle. Idle mix screw is at 3 turns out. The 2005 T100 already has the Thruxton needles. At this point I have no flat spots, good throttle response, and get an average of 42 mpg on country, highway, and mountain riding. I would suggest that you replace the manifold nipple plugs regularly as they seem to be quite prone to cracking. I also put small clamps on the plugs to hold them in place. I would also suggest that you try one, then maybe two 0.5 mm shims on the needles, as this is a frequent fix for flat spots. Finally, I would suggest that you take the pilots back down to 40 to see what happens to your mileage. You don't say how much you use the choke, but I have found that at 80 F and above, the bike hardly needs choke, and at 60 F and below, it only needs about three-quarters choke for 30 seconds, then ride half a mile or so at just a bit of choke, then off--and a bit more choke below 50 F. Probably obvious, but I'll mention it: tire inflation. I am a bit obsessive about this (dad was an engineer at a tire company) and while it hasn't gotten me great tread wear at the rear, it may account for the better mpg. My bike has 5600 miles and I'm planning on replacing the rear Metzler by 6000.

dazco · 10-23-2005, 06:11 PM

T100=thrux needles......didn't realize that ! Well, as BR said, i too would suggest shims. I tried one shim on mine recently and it really helped the midrange. 2 didn't make any difference tho, but again i have a speedmaster. But in any case i would definatly shim those needles with one and 2 and see what works.

DrMath · 10-23-2005, 08:26 PM

:-D Thanks for the great replies.

First I have 3800 miles on my bike. Also I forgot to mention I have NH Togas installed no baffles.

I did notice some cracking on the nipple uses to replace the hose from the AI. I read in a few other threads about replacing the manfold nipple plugs and using clamps. I think I'll do that.

I was thinking about going to 40 pilots with 2 1/2 turns. I definitely will add the shim.

I only use the choke to get her started and warmed up about 3 minutes, then the cloke is off.

As for air, I check them about once a week.

DrMath · 10-23-2005, 09:01 PM

:-D Just got back from the New Bonneville site and can't find manfold nipples. Is it an OEM part that has to be ordered thru the dealer or does anyone know an equilent part.

BillT100 · 10-23-2005, 10:16 PM

DrMath,

If your manifold and carb caps aren't cracked you can just put a clamp on each one or wind some fine wire around them and tighten with a pliers. You can find these caps at auto parts stores but they usually aren't as thick.

I would suggest replacing the manifold clamps with worm clamps that can be found also at auto parts stores, but the right width may be a little hard to find. The worm clamps I used are size 28, stainless steel and 11mm wide. The stock clamps really can't be tightened sufficiently and sometimes are a source of vacuum leaks along with the manifold caps. I believe Newbonneville and Bellacorse have the replacement manifold clamps if you don't want to shop around for them.

Bill

RedBird · 10-23-2005, 10:47 PM

I gave up on purchasing vacuum caps from auto parts stores--couldn't find any that would last more than a couple of months. I ordered 6 from the Triumph dealer--problem solved.

What was your mpg prior to installing the NH Togas and rejetting?

Larry

DrMath · 10-24-2005, 03:59 PM

Redbird, before I did the mods (NH Togas, AI removal, and rejetted) I was getting 42-48 mpg.