[Heavy Duty Mick]

Lots of differing opinions here.

I don’t care if anyone likes or dislikes what I have done.

This bike makes me smile every time I ride it and that’s all I care about.

If other people choose to use any info that I have shared, that’s another reason to smile.

If people choose to disagree, that’s good too. If we all agreed, it’d be a very boring world.

[twocoolgliders]

Yo dude!   You actually "did something.....not just idle talk....you did it!

Cool!

The information is very useful.

Hopefully you are happy with the results and it met your expectations!


Cookie
 

Lots of differing opinions here.

I don’t care if anyone likes or dislikes what I have done.

This bike makes me smile every time I ride it and that’s all I care about.

If other people choose to use any info that I have shared, that’s another reason to smile.

If people choose to disagree, that’s good too. If we all agreed, it’d be a very boring world.

[mwmosser]

For sure. Was just saying in another thread that if you're happy with it, that's all that matters. Thanks for posting your experience and enjoy riding!

[Oldie but Goldie]

Thanks for sharing

[cyril31]

Seems i was not understood.

I find your results interesting, and totally in line with what i would expect from that work. I have nothing against people who mods stuff as long as they make an informed decision, and in this aspect, your post is very welcome as it shows exactly what you get, and the info does not come from someone trying to grab your money.

The message i try to say is "people should do these mods if cost is not an issue, if they are not aiming for more than 3-5hp, and if they do not mind not being road legal".

I would not do it on my bike, mostly for the first 2 reasons to be perfectly honest. But i have absolutely no issue with people who do it anyway.

[Dr Mayhem]

Think I measured the runner length in the airbox at 9 1/2"with a total of 14" to the valves. Cut that total intake length to 11-12" and you get over 50hp without loosing anything (very little) on the bottom.

That HP curve is 99.8% because of the stock 14" intake length

[Dr Mayhem]

As good a explanation of long intake runner vs short as you're ever likely to hear. This is a universal truth among all 4 stroke engines regardless!

Love those TPI 383 strokers. I have one in my old GMC box van 

https://youtu.be/QazvSzZKj24?t=326

[dcolak]

Guys, are you aware that top torque of the original bike is at 5100 RPM?

Modified one gives you that same torque at 3500 RPM!

Modified bike at 6500 RPM still gives the max torque that original bike had at 5100 RPM!

That is simply AWESOME.

It transforms the bike from good to awesome, if you actually like to ride it and are not afraid to use the full RPM range 

Ah, and if you ride it like granny, you still get the benefit of having max torque at low 3500 RPM, which actually does not fall off afterwards but keeps rising (unlike the original after 5100 RPM).

P.S.
You do not do this kind of mod to get "3 HP on top."

You do it to get more useful torque all over the RPM range and actually keep the motor more relaxed.

[Starpeve]

Think I measured the runner length in the airbox at 9 1/2"with a total of 14" to the valves. Cut that total intake length to 11-12" and you get over 50hp without loosing anything (very little) on the bottom.

That HP curve is 99.8% because of the stock 14" intake length

Can you suggest any simple reversible way
to shorten the runner?
Steve

[NVDucati]

Can you suggest any simple reversible way
to shorten the runner?
Steve

A rotary saw and JB Weld   

[Starpeve]

A rotary saw and JB Weld   

Couldn’t just plug it somehow? Does the chamber have to be rigid?

[Dr Mayhem]

Posted by: dcolak
« on: Today at 01:40:36 am »

    Insert Quote


Guys, are you aware that top torque of the original bike is at 5100 RPM?

Modified one gives you that same torque at 3500 RPM!

Modified bike at 6500 RPM still gives the max torque that original bike had at 5100 RPM!

That is simply AWESOME.

It transforms the bike from good to awesome, if you actually like to ride it and are not afraid to use the full RPM range 

Ah, and if you ride it like granny, you still get the benefit of having max torque at low 3500 RPM, which actually does not fall off afterwards but keeps rising (unlike the original after 5100 RPM).

P.S.
You do not do this kind of mod to get "3 HP on top."

You do it to get more useful torque all over the RPM range and actually keep the motor more relaxed.

YES!.. good advice!!

Quote from: Starpeve on Today at 03:22:24 am

    Can you suggest any simple reversible way
    to shorten the runner?
    Steve

Component parts all glued together so it would be a little involved

[Bilgemaster]

Here's another vote of thanks to the pile for 'Heavy Duty Mick' for going to the trouble to document his performance gains so masterfully. In fact, with my newly-acquired magical powers of "Global Moderator" I find that I was able to award him a well-deserved "Karma Point" for his efforts.

I may still be plodding along on an old Iron Belly thumper, but still find your modern 650 shenanigans fascinating. The Interceptor's at the top of a very short list of bikes built since the Reagan Administration that I'd like to own one day. So far I've only ever seen a single one "in the wild", an Orange Crush one that also makes it to those 'Bikes and Breakfast' shindigs in Clifton, VA. The only thing I find uninspiring about it is its overly subdued exhaust note. It's a little TOO restrained and "wheezy". Hard facts aside, the heart can't help wondering how "Heavy Duty Mick's" ride sounds with all those farkles. A little more full-throated, perhaps? I wouldn't want to rattle the neighbor's windows when I set off. Hell, my Bullet's still running stock pipes to keep it kind of subdued when need be. But just a little low-down bark when you give it a twist would be nice.

[tooseevee]

It's also emission standards. Not going to get into a flamey kind of discussion about all that, but Euro 4 and Euro 5 emission standards are tough for a reason, and they are the global standard (even more than EPA). Yes, bikes are a small percentage of overall vehicles on the road. Yes, diesel trucks and lawnmowers and any big ICE is going to be emitting more than any of our no-longer-compliant bike with a cat delete and re-tune.

Yes, bikers are notoriously independent and crotchety and hate to be told what to do  .

All that does not change the fact that manufacturers are making bikes to meet emissions requirements. We're free to modify as we wish. But engineers have to design to standards that allow bikes to be sold.

           Well said.

[cyril31]

Guys, are you aware that top torque of the original bike is at 5100 RPM?

Modified one gives you that same torque at 3500 RPM!

Modified bike at 6500 RPM still gives the max torque that original bike had at 5100 RPM!

That is simply AWESOME.

It transforms the bike from good to awesome, if you actually like to ride it and are not afraid to use the full RPM range 

Ah, and if you ride it like granny, you still get the benefit of having max torque at low 3500 RPM, which actually does not fall off afterwards but keeps rising (unlike the original after 5100 RPM).

P.S.
You do not do this kind of mod to get "3 HP on top."

You do it to get more useful torque all over the RPM range and actually keep the motor more relaxed.

This is a mistake, but do not worry many people do it. A WOT dyno run cannot be used to extrapolate part throttle or transient as you imply on your last sentence. Unless you get more displacement, the additional power at WOT is always the result of lesser power at part throttle.

The engine lost its harmonics scavenging systems both at the intake and exhaust to get more flow when it was limited, i.e. at high throttle opening and WOT. This means the engine will give more torque than stock, but only at that time; and it will give less when these systems were working. There is threshold on the throttle opening where the power is going to be worse than stock. Usually that is under around 60-70% throttle opening.

It means that when you are cruising, or giving a bit of gas, the engine will produce less torque than stock. the upgraded air filter gives better transient, which makes the butt dyno feel that you get more, but you do not. While this is great in racing condition, it also makes keeping the same speed harder; the bike becomes a bit more on/off.  It is similar to how stiffer suspensions can make its user believe he goes faster, as he feels more bumps and Gs. I had quite some passengers in my track car that said it felt slow compared to their car. They were very surprised seeing it was actually running 2 seconds a lap faster than them. Do not be deceived by your feelings !