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I am a first time rider and have had my 2007 Triumph Speedmaster for 2 months and mainly go around urban area with top speed of 60MPH. This past weekend I went on a long ride in the country with speed limits of up to 75 MPH but could not get my bike to go above 65-70 MPH. The 3rd gear is the gear that I was in to get up to that speed and at times was up around 6000 RPM. If I shifted into 4th it would maintain that speed with around 4000 RPM but would not going any faster. So my question is what would most likely be the issue. I am thinking I should try the jetting first, but just wanted to see what others thought. Also I am a big guy at 250lbs, but was thinking the bike should still hit 90 MPH.

Have you synced the carbs, checked valve adjustment, have a different intake and exhaust from stock, how many miles accrued, etc, etc? We need data, and then maybe we can help you break into the 70MPH zone. Even at 250 Lbs, your bike should do the ton, after that it's a matter of defeating poor cruiser aerodynamics.

The bike only has 3400 miles on it but the guy I bought it from did say he had it rejetted so that is on of my fears is that it may be running too rich. He also said he had synced the carbs but I have not checked the valve adjustment. Everything is stock in the way of performance except a Uni air filter.

The jets issue is a valid concern, but what exhaust are you running? There is a jet calculator in the vault that's a guideline for airfilter/ exhaust combinations. But you have to ascertain what's in there now. Your valve lash should be fine at 3400 miles. The airflow thumbscrew adjusters are a good investment too. $39 from FastEddy.

That sounds like one (or maybe both) of the carb diaphragms might not be seated properly under the tops and leaking air. That's really easy to check by removing then tops and insuring those sealing ridges are seated in the recessed groves. It can be tricky to get them just right because the material will swell from contact with fuel and then they try to wrinkle when you put them back in. if that's the case they'll shrink back to size overnight if you leave them out of the body in a dry clean place.

Welcome aboard Jason. Hope you get it sorted soon

Thanks everyone for the quick response I think Oldroadie might be on to something. Also everything recommended seems fairly quick and inexpensive to check/replace so I will update when I try some of these out.

Also it has stock exhaust.

It's gotta be a carb issue. These bikes will do a ton easily, and my wife and I rode ours at 85 to 90 many times.

Jason's not that much heavier than me so the bike ought to run fast, and, be able to hit the rev limiter. I suppose it could be way over-jetted or have the TPU really out of whack but the diaphragms are such an easy check and can act as rev limiters I though that was a good first step. One thing's for sure, that UNI filter isn't any advantage with the stock muffs, that's only half the breathing improvement...needs at least TORs in combination to do any good.

I am 225 and I have no issue hitting the rev limiter or the ton with Melody on the back.

When mine did that it was the little hidden fuel filter between the carbs. If its still there, pull it out and throw it away. Put an in-line filter in the fuel line.

Jason, like others have said, something is not right with your engine. Get it fixed up and you'll love the power these twins make!

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The stock filter is tiny. Not much surface area. Looks like a tiny sock that wouldn't fit over the end of a ball point pen. More than a few members here had trouble with it. Whether its cleaned, replaced, or ditched for an in-line, its probably the culprit.

One of the two things I ditch right off the bat, the hidden filter and the tip over valve. Both have left me stuck along the side of the road, once and only once..

Jason, what sprocket do you have in front? IIRC, the Speedy has a 16T or 17T. If the previous owner swapped that for a 19T (and you have a large windscreen) that might contribute to your problem.

Add a hot day and your speed will be affected. Not as extreme as 65-70, but noticeable.

Tried taller sprockets, sticking with my 16T.

A 17T along with a 43T rear is the best I have found. At least in up and down country. Which equates to 4.75 Froghairs taller than the 16/42T combo.

FIXED!!!!

Well I got around to working on the bike today and took off the carbs and inspected everything. I also tried to find the hidden fuel filter but could not find it so thinking previous owner had removed. The issue ended up being a completely clogged main jet in the left carb. I put everything back together and it is a completely different bike now. I just rode around the block but based upon how fast it was compared to before even at the low gears that I can hit the ton now. Thanks for everyone's comments and loving my Triumph now even more.

Great to hear....

If the hidden filter is missing, you need to get an inline filter in place otherwise you will end up with more garbage from the tank clogging your jets.