Passing power?

G

GuyM

Street Tracker
Rode with a little pack of sport bikes yesterday. An Aprilla 750, and a variety of Yamahas, R6, a couple of bigger liter bike versions and a Honda VFR 800. Lots of fun and the stock Scram held it's own fine on the twistys and on the back roads.

When we got out on the highway heading home though - the pace quickened and we passed some slower traffic. Several times. Those sport-bike critters have sure got it all over the twin for passing power... "Vwoop, gone."

So - will a set of pipes (I'm thinking TOR's), a better filter and a good tune help with the 50 - 80 mph acceleration? Okay, maybe to 90 for the occasional pass?

Or will the Triumph just growl louder and not accelerate any quicker?

Thanks, Guy
 
rmak

rmak

moped
Well, Guy, there's good news and bad news. The bad news is that even with my airbox out, TORs and rejet, etc., my buddy's 620 Multistrada can out-accelerate my Scrambler throughout the power band. The good news is that his Ducati looks like a yellow preying mantis and the Scrambler....let's just say it's a thing of beauty. My guess is that the majority of the people who bought Scrams didn't have in mind head-to-head competition with higher tech bikes.

Most of us are looking for potential extra power we know is there. I think you're right to start with the easiest and cheapest-intake and exhaust modifications. That's what I did, and I'm happy with the results for now, but I see a lot more speed upgrades in the future.

To your question, from my humble understanding of carbs, the main jets are what fuels the engine with wide open throttle, so bigger main jets and relieving any intake and exhaust contraints (filters &TOR's) will increase your top end performance. But I'm just a back yard mechanic, so I defer to anyone with a more technical answer.
 
G

gilligan

Scooter
Guy,

I own a BA, so I can't give you specific recomendations for a scrambler, but my experience is that these bikes respond really well to pipes, jets and airbox mods. I would first invest in an aftermarket pipe. The TORs will be quieter than most other systems but might not give quite as much benefit in terms of power. Still, I have TORs on my America and it runs great. So you spend the money on a pipe, and then pull the snorkle out of the airbox and get a uni or K&N. For jetting, if you go with TORs I'd start with one main jet size higher than stock, so if stock is #115 go to #120, if stock is #120 go to #125. This is a starting pont. If you get an aftermarket pipe, you may need to go up two sizes on the main jet. Then, I'd try putting a shim under the stock needle, so your midrange is not too lean. Then Test ride and see how it feels, adjust from there. If you have not already checked out the Dinqua site, do so and it will explain the details of rejetting. You don't have to remove the carbs, you can pull the bowls off with them attached its a PITA, but it can be done. Once you get your jetting sorted out, your bike will feel noticably stronger. Not sure your going to be able to run with VFR's and Ducatis, but at least you will be able to make a safe pass on a narrow road.
 
G

GuyM

Street Tracker
Roger that. Understand I'm not going to run with the fast multi-cylinder sport bikes. Used to ride a 750 Suzuki and miss the way that power used to build as the revs rose... The Scrambler starts out surprisingly well at lower speeds, then seems to pretty much run out of ooomph at higher speeds. I'm just looking to perk 'er up a bit at higher speeds for better passing on fast two-lane highways.

That Aprilla 750 "Shiver" was a pretty neat bike on our recent ride - quick, looked good, seemed to handle really well and sounded pretty good too.

I think I'll ride as-is for the rest of the year then take on pipes/jetting this winter when I've more time to spend doing a little work on the bike...

Thanks, Guy
 
Old Scratcher

Old Scratcher

who?
My Scrams putting out over 70hp, after having truck loads of money spent on it. & while it's a lot faster than stock, & even more fun to ride. It's still nowhere near as quick as my unmodified Street Triple was, straight out of the box. It's also heavier, slower-handling, & grounds out it's pegs a lot sooner. But I still wouldn't trade it for the world.
 
G

GuyM

Street Tracker
Exactly O.S. - I'm not going to try to turn it into something it's not - just perk it up a little... Love the Scram, it's a great little bike, friendly and always ready to go. Not that the sport bike riders were hauling a** - but they didn't slow on the twisty sections to accommodate me. Yet the Scrambler kept up just fine on the backroads - it was only out on the highway that their acceleration really showed as an advantage.

No 904 kit right now - but that does look like a great way to pump up the power quite a bit.

Later, Guy
 
G

gilligan

Scooter
All of these bikes are jetted too lean from the factory to pass emissions. The jetting change is not that hard especially if someone who has done it before shows you how. Plus, once you put the pipe on, it's cheap - jets and a Uni filter will cost you less than $50.

Best thing I ever did to my bike.
 
C

Canucks_Fan

Scooter
With exhaust, re-jetting, AIR removal, and K&N my Scram went from 49 bhp to 62- the torque (that passing power you want) went from 51 lb-ft to 63- a HUGE difference considering I have less than $500 total for that much performance increase. These mods will not just make it sound better! That said, we need to meet up so you can ride mine and feel the difference!
 
rmak

rmak

moped
Canucks_Fan said:
With exhaust, re-jetting, AIR removal, and K&N my Scram went from 49 bhp to 62- the torque (that passing power you want) went from 51 lb-ft to 63- a HUGE difference considering I have less than $500 total for that much performance increase. These mods will not just make it sound better! That said, we need to meet up so you can ride mine and feel the difference!
Click to expand...

Is this dyno figures or just seat of the pants? If you have this documented, you have made me a happy man!
 
C

Canucks_Fan

Scooter
Dyno'd- for only $25! Was at a local dealer that was having a stunt show and they had a guy doing mobile dyno's. The weather on the day turned out to be 35 degrees with horizontal rain, so the few of us that rode got the test for $25 vs his normal $100.
 
G

GuyM

Street Tracker
That's a huge increase without getting inside the engine. Wow! Which exhaust did you use? There's a fellow here in town with a dyno - he's done a Bonnie, and I think I'll head his way for a good tune, once I figure out which exhaust to use.

I'm glad you didn't lose any of the torque that makes these bikes so good - it's got to feel great with the increase!

Thanks for the info! Guy
 
C

Canucks_Fan

Scooter
Cut the heat sheilds off and patched the holes. I didn't like the looks of the stock shields.

P1010205.jpg
 
NEPatriots9

NEPatriots9

Scooter
I've got the Thunderbike complete exhaust kit on the way, coupled with an upcoming airbox removal, should be done in a couple of weeks.

The guy who is doing the work is going to dyno it as well, so I will keep you guys updated.
 
rmak

rmak

moped
Canucks Fan,
I gotta tell you, buddy, I've been reading your posts over and over and I'm really confused. The heat shields bolt on the the TORs, so what exactly did you cut off? They sure do look like Norm Hyde slip ons
http://www.normanhyde.co.uk/search.php?start=31&stop=41&tag=14&parent=. If you can make TOR's look that good, you should go into business.
Since I'm asking questions, what is a .020 jet? The main jets usually are numbered 110, 115, 120, etc. Thanks in advance for clearing this up.
Rich
 
C

Canucks_Fan

Scooter
P1010381.jpg
As to the exhaust, I guess I don't really have a clue what they are if they are not TOR's. They were sold to me from the dealership, they came in a box that says that they are Triumph silencers, and I used a part of the $1k they offered for accessories to buy them, but I guarantee that the shield mounts were welded on. All I did was cut the mounts off, patch the dimples, re-chrome (free via work), and remount. As to the re-jet, I used a micrometer on the old ones vs the new that came with the TORs and there was a .020 difference in the diameter. There wasn't anything in the paperwork that stated a size, other than a single 2" X 2" piece of paper in the package with the jets that said 15. No idea if it was inspector 15, part number 15, or size 15, so I used a micrometer for my own future reference, hence the .020.
 
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