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Hello All.
I have been riding motorcycles for 20 years. Namely....a 1975 Honda CB-750 Super Sport & a 1980 Honda CB-900 Custom. Both inline 4 cylinder keihin carbed bikes. I just purchased about a month ago a Triumph 1999 900 Adventurer. I had been looking at these "new" triumph triples since 1994 when they were being brought back into the market in North America. I was at the time not able to afford a new bike. So I have been waiting for this generation of bikes to become older and come into my price range. So now I am the proud owner of one and am somewhat frustrated by the experience. The bike is beautiful, and I love it......but I cannot get it to run in the manner I am used to with both of my Honda's. It idles fine. But upon acceleration....at around 2000-2500 rpms it stumbles........seems to like to be run up around 3000 and beyond. Not sure if this is a characteristic of these bikes or not. But upon reading countless posts........I am becoming disheartened at how much screwing around with these bikes everyone seems to be doing. Both my Honda's ran flawlessly. Idle to hard acceleration..........to doing over 100 mph. These are 35 and 30 year old bikes. I buy an 11 year old bike......and it can't claim the same. Furthermore.......I read post after post of people changing jets....airbox arrangements, shimming needles, replacing coils/ignitors.........what is up with this????
I have pulled carbs apart. Stock main jets....no shims....pilots at 2 1/2 turns out. Did not remove pilot jets to confirm their size. Stock air filter. Triumph Off Road Mufflers. Bike pops like no tomorrow on downshift. Has a stutter on acceleration around 2000-2500.....I've change plugs to stock plugs....to no avail. I am very familiar with teardown of carbs etc......mechanic by trade. Are these bikes unable to run with smoothness and consistency of Honda's??? I don't want to spend countless hours chasing something that is unachievable. The bike has tons of power, and I do love it. But am I being unrealistic expecting it to purr like a kitten through all speed and load ranges like honda's do???
 

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Well, your main problem sounds like it is in the pilot jet range, so it seems to me you are having a problem because you have avoided the problem by not removing and cleaning the pilot jets. Pilot jets are operating in the 1500 rpm to 3000 rpm range, then you kick into the mains.

You bought an 11 year old bike, not a new bike. All these bikes ran flawlessly when new. How many miles are on this machine? I suspect you have purchased one that has sat up a bit. It has the same carbs as your Hondas essentially. Problem is, you probably don't know how they have been cared for.

Many people buy Hondas for mundate reliability. They usually don't get hopped up that much, though some of the cafe racer crowd has taken a liking to the CB750 these days. I believe Triumphs attract a bit of a different breed. You see people fooling around with T-Birds and the like because they want to get more power out of them, and know the engine is easily capable of 100 hp with stock parts. This engine was run in everything across the early modular platform, and produces anywhere from 69 hp to 115 hp in different configurations. Problem is, there was a lot of engineering that went into airflow design to make each motor perform the way it did (in this modern age of low emission regulations), and as a result, getting a T-Bird to perform like a Daytona takes some significant engineering on the part of the builder.

These bikes are better in every way that the old CB, IMHO, and I owned two of those bikes (and they both blew up on me...) I have often referred to it as an improvement on the CB - performs and handles better, more exciting to ride, with triple attitude.
 

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My 900 gives smooth and strong power at all RPMs, no mods, just regular maintenance of the stock config.

I'm gratefully that Triumph is embracing the clean simple lines of that CB era AND we get in a technologically updated package.

I'm a big fan of the Honda CB style. When I imagine a motorcycle I see a CB. It's what the guys in my neighborhood rode when I was a kid. But Honda abandoned that style 30 years ago (in the US). I don't count the Nighthawk 250/750 styling. I can guarantee you that not every CB out there runs a good as yours did, I know 'cause I looked at a couple of ragged out crap wagon CBs that pushed me to a newer bike.
 

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The Triples are running borderline jetting, and sometimes it gets to the wrong side. For instance, my brother's Daytona - 100% stock - didn't tolerate full throttle until 6000 rpm without bogging.

You had the same thing with bikes from Japan back when, EPA regulations forcing them to be run so lean that when things aligned in a wrong way, they had running issues.

I would try first to turn out the idle mixture screws 3 turns, maybe 3.25. If that doesn't cure it, raising the needles one notch (about 1.5mm) should.
 

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let's not forget that he may have a coil going bad.
Let me rephrase that: he probably has a coil going bad.
 

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The triples should run silky smooth and clean all the way to redline.. All this messing with jets and airboxes that you read about is people trying to "improve" them. Bikers are inveterate tinkerers.
 

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l agree with Cafetbird , l have just come back from a 1oo mile run ranging from motorway, country lanes and threading though traffic jams in London for 3 miles and the Tbird ran faultless throughout the rev range. it also has the smoothest gearchange of all the 30+ bikes including ten Honda ( my present Honda is a TransAlp). Its those pilot jets not any design fault. l also get better gas mileage than the TransAlp, how come??.
 

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Discussion Starter #11
Thanks to all of you who chimed in. I will likely take the carbs off one more time and remove the pilot jets. For 2 reasons. First to find out if they are stock (38). And to put to rest whether they are really clean or not. My 20 years of biking and 30 messing with engines leads me to eliminate the carbs first before thinking too much about the possibility of maybe having a bad coil. But I did blow compressed air through all orifices when I did have them apart, and had flow through them all. Don't get me wrong about what I was saying.....It was an honest observation. I love the triumph and am confident I will sort it out. Just after 20 years of riding 2 inline 4 cylinder hondas with keihin carbs I never ran into any problems. I would have thought these bikes would be technically more advanced being 20-25 years newer & I am disappointed in hearing things like...."after 7 years I've had to replace my coils" ....carbs needing to be dismantled and cleaned several times on a 8-10 year old bike. The whole air cleaner scenario is ridiculous, as has been hashed many times on this site. Love the styling, love that Triumph isn't just pumping out Harley clones......and I fully intend to stick with my adventurer. Love it. Let you know how I make out over upcoming weeks.
Thanks
 

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The bikes were fairly technologically consistent with any affordable early ninties machine from wence they were designed. 4 valve, dual overhead cam, electronic ECU, rear monoshock - pretty standard stuff for the time. They were trying to be a bit retro, afterall! TBS gave a few extra niceties.

As for the coils, that is a very minor issue, IMHO. I had to replace coils on 2 of the 3 Hondas I owned also.....

And yes, Al, the most difficult electrical problems to diagnose on these machines is a carburetor issue.
 

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Unfortunately the era these bikes were built is like the early '70's was for Automobiles. The EPA regulations do not favor carburetted engines. Triumph is not the only carbed bikes of that age that need sorted. But hang in there sounds like you have the knowledge to get it worked out. It is worth the effort.
 

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And yes, Al, the most difficult electrical problems to diagnose on these machines is a carburetor issue.
He said most carburation problems are electrical, not the most difficult problems to diagnose.

Seems like the biggest carburation problem with a bike that has been sitting for a while would be crud.
 

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hi there just wanted to add my 2 cents worth on your rant if you dont have the history of the bike ,try running some of the stuff called startron enyzme fuel additive throu a full tank of fuel(gas) see how u go i feel that it is a fuel prob and not doing the pilot jets maybe you could have missed the prob,i can only go with my bike i ride , that u can read in my thread thunderbird 900 starting promblems ive since resolved the prob as when it went to my local dealer they ommited to put one of the carb balancing caps on and it run like a bag of bolts ive rectified this prob now and she runs a dream no popping on down shifts ect mpg up gear change and smothness up i hope this helps u as ive said in my threads im indebited to the guys in this forum for there advice and with the help i got ive looked in places i nvr thought of good luck and i hope you find wats up real soon cause wen they run perfect the t bird is the dream bike
 

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Stumbling at 2000 to 3000

My bike had the same problem. I checked the the jets and adjusts valves and it still did it. Then I resealed the airbox and the bike came alive. Now I can go from idle to WOT without even a hiccup. If you take in account what cafetbird said about airflow design then these bikes prefer sucking air through a straw.
 

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My bike had the same problem. I checked the the jets and adjusts valves and it still did it. Then I resealed the airbox and the bike came alive. Now I can go from idle to WOT without even a hiccup. If you take in account what cafetbird said about airflow design then these bikes prefer sucking air through a straw.
Did this involve gasket work/replacement, or something different? I notice a bit of a stumble as well, but it might just be I'm asking too much before the engine's properly warmed.
 

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Did this involve gasket work/replacement, or something different? I notice a bit of a stumble as well, but it might just be I'm asking too much before the engine's properly warmed.
No gasket work. The carbs were just getting too much air. It was sucking it through seam where the airbox splits so, I applied some silicone caulk. My bike doesn't even stumble when it's cold. It's a whole new bike now.
 

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No gasket work. The carbs were just getting too much air. It was sucking it through seam where the airbox splits so, I applied some silicone caulk. My bike doesn't even stumble when it's cold. It's a whole new bike now.
Probably not excessive air, but air flow disturbance. What little air can leak throught the tiny cracks in the airbox (unless they were really big?) is unlikely to affect jetting noticeably, but it could easily create vortexes that upset jetting.
 
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