Bonneville America Forums Forums Technical Forums Performance Mods Rejetting Help?

Forgive me for double posting this question but not sure the New Jet Calculator thread was the best place to post. I'm getting conflicting advice on the correct size mains I need to rejet and wanna make sure I got my ducks in a row before attempting this myself. Not sure I'm using calculator correctly. I have a 05 speedy with D&D pipes, airbox and AI removed, K&N pods, 1,000 feet above sea level. I'm assuming the needles and pilots are stock since the only previous mods were the pipes and a rejet from dealer. I've been told 150 or smaller, 160, and I'm getting 154.5 when I calculate. Does anyone have a similar setup that can make a suggestion? i would appreciate any advice. also does the 2005 require the "D shaped" tool when rejetting?

Not sure how restrictive the D&Ds are but if it helps I have a similar set up otherwise and run a 155 main and 48 pilot. You will probably want around a 150 main and 45 pilot. That would be a good place to start anyway.

the o5 does use the "D" tool for adjusting pilot screw. but not to replace the jets you want to install the jets then screw the pilot screw all the way in and then turn it out 2&1/2 turnes to start with.
the problem with re-jetting is that there are several stages that the carb picks up fuel from the bowl. At first or start up from idle or zero throttle threw about 1/4 throttle is all the pilot screw then at about 1/8 throttle the pilot jet kicks in and adds some fuel through out the range till full throttle but not much after the 1/4 throttle position.
From 1/8 throttle through about 1/2 throttle is affected mainly by needle diameter, then from about 1/4 throttle through about 3/4 throttle is affected mostly by needle shiming or clip position. About half throttle through about nearly full throttle is affected by the needle taper, and the main jet picks up from 3/4 throttle to full throttle.

I hope this helps you to understand carb set-up. a little better.
http://www.triumph-bonneville.com/images/TN4.pdf

You can take the pilot screw out and cut a slot in it to use a screwdriver or buy thumb type screws or even buy slotted screws. You can also take a piece of brake line and flatten one side to make a D tool.

Then disconnect 1 spark plug wire and ground it then adjust the idle so the bike runs on the remaining cyl. Turn the mixture in until it runs rough then back out until it runs rough again. The correct setting is 1/2 way between those 2 points. Do the same for the other syl. then adjust the idle with both cyl. hooked back up. Don't spend too much time on this for one you don't want the engine over heating and you don't want to dump raw fuel in the engine and not burn it. You can do the same thing with both plug wirs connected but it is much harder to determine when the cyl. you are working on starts to run rough.

its more difficult but thats the way I would do it. also when you get what you think is close. you can take it for a run, If you get poping in decel you can rich them up some like 1/4 turn at a time.
step two is balancing because it is very easy to have one slightly richer than the other. now I am not talking vacumn balance if you dont separate the two carbs they should remain balanced in that way.
a good way to start is one of those lazer temp readers. allow the bike to cool all the way down so you feel no heat when you touch the header pipes. then start the bike and let it idle for about 1 or 2 minutes so that with your hand you can feel the header getting hot. then use the temp reader and check each header pipe if one is hotter than the other it is richer. adjust the the screw untill they read the same by repeating the step.

One getting hotter than the other is more likely balance than mixture screw.Although mixture being way off would do it too.

If it's a rich/lean condition, the side that is hotter is leaner than the other side... ,or,... the other side (the cooler side)is richer than the side which is dialed in correctly.

If you have the vacuum balanced wich is to say that while you open the throttle you pull the same on your gage that is attached onto the intake manifold. if not there is a screw that adjusts the linkage.
now if one has a little bit more gasoline in the mixture the combution will be hotter. because the air is air not oxygen. If you pour more gas on a fire it gets hotter.the one that is hotter is richer. and even a very small amount will affect the header pipe right at the head. now I am also talking about to small amount to feal with your hand. However dont idle too long because they will balance out. only idle long enough to feel warmth building in the header pipe and stop while it is still cool enough to keep you hand on it with out burning your self. then because the combution is hotter you will get a small temp difference could be as much as 5 degrees. That is why to use the lazer rather than just your hand because it is difficult to feel that small of a difference.

wow that post is full of typos but i dont feel like editing it maybe tomorrow

Thanks for the info guys!

Always make any adjustments at operating temperature though. If you are going to do much adjusting with the engine running get a couple big fans blowing on the engine or give time to cool some between operations. I use a box fan when balancing but adjusting mixture I normally don't have it running long enough to worry about it.Balance then adjust the mixture.

http://en.wikipedia.org/wiki/Air-fuel_ratio

5t paragraph down...

Lean mixtures produce hotter combustion gases than a stoichiometric mixture, so much so that pistons can melt as a result. Rich mixtures produces cooler combustion gases than a stoichiometric mixture, primarily due to the excessive amount of carbon which oxidises to form carbon monoxide, rather than carbon dioxide.The chemical reaction oxidizing carbon to form carbon monoxide releases significantly less heat than the similar reaction to form carbon dioxide.(Carbon monoxide retains significant potential chemical energy. It is itself a fuel whereas carbon dioxide is not.) Lean mixtures, when consumed in an internal combustion engine, produce less power than the stoichiometric mixture. Similarly, rich mixtures return poorer fuel efficiency than the stoichiometric mixture. (The mixture for the best fuel efficiency is slightly different from the stoichiometric mixture.)

Thats logical, I have to concede to greater logic. So there fore my friend the hotter is leaner as Two wheel n has proven per the book . D@mn it I forgot what the book said. Sorry, I made a mistake in trying to reason in my head rather than just looking it up . The hotter side is slightly lean but not much we are talking 1/8 turns to the screw here.

Still balance first to avoid a false reading due to the butterflies not opening evenly causing one side to be hotter due to that rather than mixture. Then adjust as I stated above to get the correct mixture. You can adjust a little to the rich side if you have too much popping with less restrictive pipes.

yes I agree, I was assuming that the balance work was done all ready. Thats the first thing to do when you get a bike because the dealers don't do a very good job of setting them up.
Then if you pull the carbs to put the jetts in you don't have to separate them. Then you shouldn't have to rebalance the butterflies.

I think it is a good idea to pull them the first time to familiarize yourself with where everything is if you have never done this before.

for the mechanically inclined I agree. some people should just leave it guys like you and me.