1995 Trophy 900 mid RPM Stumble - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 9 (permalink) Old 05-04-2019, 01:54 PM Thread Starter
Grand Prix 125
Main Motorcycle: 1995 trophy 3
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1995 Trophy 900 mid RPM Stumble

Just as the title says. The bike pulls amazing down below 4500rpm. At 4900ish, it starts to stumble and does so all the way to 9500.

What I have tried thus far:
New plugs
Chased vacuum lines
Rebuilt petcock
Put fresh gas and some carb cleaner in it

This bike does not sit for any discernable amount of time, so varnished gas is unlikely as I also completely drained the tank when I did the petcock. As near as I can tell, the main jet or jets are clogged some how. But that leads me to my next conundrum. This is an early (by US standards) Trophy. It has the wider Exec wheels and three Keihin CVKs. Everything online says this boat should have Mikunis.

Someone throw me a bone here. I don't think coils are the issue as it only starts at 4900ish rpm. And you can actually hear the spark when it lays over. I still have my trusty KLR650 to ride and keep me sane, but a man needs to hear the cackle of a long stroke triple some times....
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post #2 of 9 (permalink) Old 05-04-2019, 10:49 PM
Formula Extreme
Main Motorcycle: 1996 900 Trophy BRG
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Other Motorcycle: 1998 Sprint Sport
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Hi Hoop, Here's a bone but you aren't going to like it. The problem is either coils or spark plug wires, or both.
New coils are expensive, used coils are a crap shoot. Same thing with spark plug wires, expensive new, crap shoot if used. Have you considered changing over to stick coils. You won't need spark plug wires and stick coils work great on my 900's. As far as carbs go, yes your bike came with Mikuni's. Some previous owner switched it over to Keihin's searching for better fuel mileage. I tried the swap and went back to the Mikuni's. I found the only carb jets that get clogged up are the idle (low speed) jets. The main jet is pretty big with the slide needle passing thru it so the main jet can't get clogged. A vacuum leak shows up mostly at slow throttle openings.

Here's another thought. The rubber carb manifolds might be wrong because of the conversion. The Keihin carbs use their own rubber manifold. Mikuni uses their own. They look very similar as if they would be interchangeable, they are not. Can you take the carbs off? Keep the cable attached to the carbs, disconnect the cable at the throttle twist grip. Then take the carbs and a manifold to Engle Motors let them check it out. By the way, I used to live in Shawnee, Ks.
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post #3 of 9 (permalink) Old 05-06-2019, 09:25 PM Thread Starter
Grand Prix 125
Main Motorcycle: 1995 trophy 3
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So from what I can tell, my bike has had Keihin its entire life. Everything is as factory and the vin matches throughout. I pulled the entire rack off and attacked the jets, mains and vacuum ports with a compressor and that did the trick. It pulls clean all the way to redline now. The boots appear to be factory as does the split face airbox. The carb linkage all looks OEM as well. The bike runs great now, possibly better than it ever has under my stewarship.

Thanks for the advice though.
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post #4 of 9 (permalink) Old 05-08-2019, 09:14 AM
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Main Motorcycle: 1996 900 Trophy BRG
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Split face air box is a mod done by a previous owner. That is one of the best mods to do to the bike. Somebody knew what they were doing.
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post #5 of 9 (permalink) Old 05-17-2019, 07:21 PM
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Originally Posted by Hoop View Post
So from what I can tell, my bike has had Keihin its entire life... The carb linkage all looks OEM as well. The bike runs great now, possibly better than it ever has under my stewarship.
Believe what you want...But they were not built that way. You just had a savvy previous owner, and benefited from his experience. Nice to pick up a well prepped bike used. My '95 had a lot of chassis improvements when I got it back in 2002. I didn't know the difference at the time. I was new to Triumph but I got a set of Triumph 6 piston front calipers, and a Race Tech prepped front fork. The front ride height had been altered to go along with the slightly larger rear tire. I have since upgraded the carbs, airbox, exhaust, etc.
These bikes, in the right hands evolve over the years. ...J.D.

Last edited by Wire-Wheels; 05-17-2019 at 11:47 PM.
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post #6 of 9 (permalink) Old 05-18-2019, 10:40 AM Thread Starter
Grand Prix 125
Main Motorcycle: 1995 trophy 3
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So it would seem. I have Sprint Fairings to convert mine at some point! So what is the advantage of swapping the stock Mikunis off for Keihins? Otherwise, mine is mechanically stock. I love it to death. Short of a Vtec VFR or a CBX1000, it makes one of the best noises ever spat out of a bike.
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post #7 of 9 (permalink) Old 05-18-2019, 02:37 PM
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The Keihin's are a bit simpler, and easier to set up. I don't really think they are any better other than that. I still have the original Mikuni's on my '95 Sprint. They have had the full jetting and tricks done to them though. I have another T-3 powered bike with Keihin's. I have done the "treatment" to them as well. Runs great. My America has Kiehin's with jetting to match the exhaust mods. No complain there either. People make too big a deal about brands. Just work with what you got. ...J.D.

Last edited by Wire-Wheels; 05-18-2019 at 02:41 PM.
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post #8 of 9 (permalink) Old 05-18-2019, 05:09 PM Thread Starter
Grand Prix 125
Main Motorcycle: 1995 trophy 3
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I guess I should have looked at the numbers when they were apart. My bike has the intake resonators removed currently, exhaust and a K& N panel.
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post #9 of 9 (permalink) Old 05-18-2019, 07:18 PM
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... My bike has the intake resonators removed currently, exhaust and a K& N panel.
Same here except for the K&N. I pulled it out and went back to the stock filter. I also have some "bird screen" epoxyed over the intakes on the air box to keep the large chunks and flying critters out. I am currently running 137 mains but I think the next time I have it apart for anything, I'll up them to 140's. These things are always a work in progress. ...J.D.

P.S. Tom Dunn. Where ever you are, I still have your Sprint after all these years.

Last edited by Wire-Wheels; 05-20-2019 at 11:56 AM.
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