Triumphrat

gm16sw · 10-09-2007

Well, once again I have carb issues.

Lately, the performance of my TBA has been less than acceptable. For some reason in low range (less than 3000 rpm) between 1st and third gear is when it is most noticeable. After around 65mph it responds alright. Anyways, the problem is that I get a lot of hesitation. The bike pulls and lags, pulls and lags, pretty noticeably. I am thinking it has something to do with the mixture or tuning of the carbs. I just pulled them off to see if the pilot jets were clogged. They seem alright. I have 45 pilots, 132 mains and tbs needles with 2 shims and UNI filter. COuld it be float levels? pilot jets? bad spark? Advice from those with similar happenings would be appreciated.

Thanks,

GM

dazco · 10-09-2007

First of all, you are running way too rich on the pilots. trust me on this, 45's are too big. I'm running a UNI too and also have the box drilled out. So unless yours is drilled then i have a more open airway then you, and yet 45's were too rich for mine and it ran like ****. dump the 45's and go back to stock 40's or at least go down to 42's which is what i run. But as i said my airbox is drilled or i'd probably be running 40's. With 40's turn the screws out to about 3 to 4 turns, with 42's use about 1 and 1/2 to 2 turns. Also drop the mains to 130's. thats the biggest you wanna be running with that setup and those needles/shims.

gm16sw · 10-09-2007

Daz,

I did that a long time ago and the darn thing popped like a SOB. SO I put the 45's back in. And no I do not have the airbox drilled out. I actually had been running fine for about a year and then all of a sudden back in June it started running really crappy but I rode it anyway and it kind of worked itself out. I did drop the bike back in April so I decided to check and see if something worked its way into the jets from being tipped on its side.

You love the carb questions don't you??

mag10 · 10-10-2007

I have been running with 45 pilots for approx 10k miles and issues with them. I think that Daz and I have similar setups. Since your airbox is not as open, you could be running a bit on the rich side, which over time could start to foul the plugs.

Since you mention the tipping thing. Do you still have a tip over valve in the gas tanks vent line? I have heard to these sticking and bouncing open and closed and giving people grief.

also, how do your plugs look?
and the exhaust, what do you have and how does the end of the pipe look?

dazco · 10-10-2007

I still think they're too rich. There are tons of things that we just don't understand such as why you ran them before w/o problems. But questioning things like that aren't always productive and we sorta ENABLE ourselves by believing theres now ay that could be the problem because it worked in the past. So i can't tell you why it worked before, but there may well be a reason. All i know is that in my bike with very open pipes and very little in the way of air restriction, 45's were much too rich and i cannot imagine how they can be right in your bike if it's like mine. If your bike is a pre 865 engine, then maybe that could have something to do with it. But even then i doubt it. I haven't seen many people stating they run 45's, and the ones that do are usually freak users. I CAN say that 45'smay run w/o any real obvious issues IF you hadn't run 42's or 40's with the same setup before that. But i had and it was very obvious it was way rich by how much performance it lost on the low end of the throttle, which by the way is where YOU are having issues ! So you may have noticed nothing if you weren't used to smaller pilots with the same setup, and maybe after a while the overly rich condition is as mag10 said fouling the plugs.

So if i were you i wouldn't question WHY, i'd just try 42's and see what happens because i know you have to be rich. He||, most people seem to use stock pilots even when modded w/o any issues ! So do what you want, but even idf they aren't causing problems, mine ran worlds better on the low end than ever with 42's then with 45's and even a bit better than 40's. 45's were just horrid.

gm16sw · 10-10-2007

I will try the 42's which is what came stock in my TBA.

Mag,

The plugs are burning just perfect. So soot, no white, just a nice yellow-brown on the ceramic and a clean electrode.

daz,

I had run the 42's in the same set up that I currently have. Like I said, the popping was horrendous so I went back to the 45's and that shut it up completely.

Mag,

I run Sceptre pipes and the end of the pipes are sooty, as they always have been. It hasn't gotten any worse or better.

I will try the 42's again and just bump the idle screws out to 4 like Daz suggested and see if that alleviates the popping problem on decel cause that annoys me more than anything.

Mag,

I am not sure about the vent valve. Where is that located in the tank? Is it accessable from the top of bottom? I assume it is in that short extension of steel tube next to the filler hole in the tank.

dazco · 10-10-2007

Ok, well i still think 45's are definatly too rich. and don't forget that jetting is interactive. It may be elsewhere that the problem exists, and popping AFAIK may also be a symptom of an imbalance in the mix even to the rich end. And with TBS and 2 shims with 132 mains i think you're definatly rich there too. If i run TBS with 3 shims it becomes a bit rich. I run TBS and i've gone back and fourth between 2 and 3 shims but i think i have 2 now. And this is with 130's. Being that you're doing the same but with a more restrictive airbox and larger mains, that too should be too rich.

By the way, many people have sworn by how accurate pat's jetting calculator is, and entering your stats the best i know shows the optimum mains as 125's with very unrestrictive pipes like thunderbikes, and only 119's with TORs. So unless the calculator is way off, your jetting definatly is. And just because larger pilots stopped the popping that doesn't mean they are correct. Some people with dyno verified correct mixture have lots of popping. With pipes and all popping is not necessarily a symptom of incorrect mixture. I'll leave it alone now, but you should consider that your jetting is quite rich in comparison to what most everyone with your setup uses. In fact, i don't recall ever seeing anyone jetting that rich with your setup w/o having problems. You may want to consider letting a shop dyno and jet your bike if you don't wish to experiment a lot more because thats what it takes to get it right yourself.

ErwinM · 10-10-2007

I run 42s and had to turn my screws out 3.75 tursn to eliminate popping. Hope that helps.

Below is a pic of your set up

gm16sw · 10-10-2007

Thanks guys, I have used Pat
s calculator in the past when it first came out. I was reluctant to consider it accurate considering no-one had been able to post positive responses about it due to its newness. I will keep tinkering with it and hopefully get it right.

Thanks for all the input.

oldroadie · 10-10-2007

Just reading the Jenks Tuning Guide everything you've posted about your set up says rich, rich, rich...the average setting for your bike would be 42 pilot, 118-125 main, one shim and air mix 2.3 to 3 turns out. Some of that depends on your pipes as well. Give the Jenks Tuning PDF a read and see for yourself...it's a great carb doc.