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Old 10th June 2010, 15:37   #16
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Originally Posted by Sankar View Post
A megaphone pipe uses exhaust pulse generated (wave) to do scavenging of the gases, and in engines with valve overlap (iirc iron engine bullet with stock cam has nil of it, exhaust opens after intake is closed) a properly designed megaphone pipe (or exhaust header in case of multicylinder) will help sucking in fresh mixture through the inlet valve during the period of valve overlap.

When glass wool is filled pulse/wave theory goes out of whack, and it ceases to be a megaphone, but just a straight through muffler with glasspack.

What i have given is just a very brief description. There's more to it.
Thanks Sankar, & indeed these exhaust pulses are the reason why its not easy to design an exhaust system. However, what you said, does this imply that the glasswool in case of megaphones obstructs the path of the gases or to say that it changes the effective design of the silencer? If yes, ideally this shouldn't happen as glasswool is used only to subdue the noise & make it a pleasant sound & not change the dynamics.
And are you sure that the valve overlap does not exist as I don't think this is possible in practicality. What I feel is that though the overlap is there, you have to tune your exhaust for a particular RPM so that this valve overlap can coincide with the negative waves produced in the exhaust or in the divergent section of the goldie design to aid in suction of the fresh fuel air mixture.

Sankar, can you post a link where we can read up all that's there to it so that it can benefit all. And while at it, I think I will read up on the megaphone & it's structure, don't think I got it right in my head.

Last edited by blackfire_9 : 10th June 2010 at 15:50.
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Old 19th September 2010, 12:30   #17
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Default Update!!!

My apologies for not updating the thread for so long with my updates...
The first thing I did was to get a metal cover made for my K&N for a local tinkering shop at shivaji nagar. He did a pretty good job, got it cut out from a damaged pulsar silencer heat shield.

K&N and carb re-jetting for bullet 500 & 350. EDIT: Chart on pg 2-air-filter-cover.jpg

In this long time, i experimented with a some silencers, one was the delhi goldie with baffles in it.Borrowed it from a friend. The thump was nice in low speeds but for mid/high RPMs, it sounded hollow.
K&N and carb re-jetting for bullet 500 & 350. EDIT: Chart on pg 2-delhi-goldie.jpg

I then ordered the Free flow goldie from Shakeel, pune. I got the glass wool separately and I decided to try riding for a couple of days without the glasswool. And good god, did it make sound!!.. The thump is really bassy and majestic till you cross, say 60, and then.. its so annoying. I cannot bear the sound once I go above 80. Forget the pillion, I bet he will surely go deaf

Currently I am running the bike with the goldie half filled with glass wool. I like it. Neither too soft like the stock silencer, nor too loud. Last week I took her to get the fitness certificate at the RTO, and the inspecting officer did not complain about the sound.
K&N and carb re-jetting for bullet 500 & 350. EDIT: Chart on pg 2-ffe-goldie.jpg
K&N and carb re-jetting for bullet 500 & 350. EDIT: Chart on pg 2-ffe2.jpg
K&N and carb re-jetting for bullet 500 & 350. EDIT: Chart on pg 2-ffe3.jpg
K&N and carb re-jetting for bullet 500 & 350. EDIT: Chart on pg 2-ffe4.jpg
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Old 19th September 2010, 12:54   #18
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Default And the performance..

As advised by sankar, I replaced the carb jet needle with a genuine VM28 one. Sankar, you were right, while running with the V24 needle, I could feel a sluggishness which accelerating in mid range(like a dead spot somewhere), now its smooth. I also got the clip position changed and now running with it mid-way (It was too low before and the bike was running very rich). Also got the spark plug replaced.

I think I have found a sweet spot now with my current setup. I am very happy with the outcome. My observations..
  • First thing I noticed after putting the free flow exhaust was the the engine became more rev happy. In fact now my third gear tops out at 80kmph, before it was at 60kmph.. (mine is old 4s RHShift)
  • Acceleration has definitely improved through all throttle positions
  • FE has not decreased. In fact It has improved. I'm getting 26-27 now (Reserve to reserve method) . This still is a mystery
  • Contrary to others' opinions, my low end torque has not decreased. I can still cruise at 30kmph in 4th gear easily. This is another mystery. Can it be because I did not change my bend pipe?

Now comping to the top end.. The bike accelerates smoothly till 110kmph (as shown in speedo) and then seems to struggle a bit. WOT took me to an indicated 120 in the speedo today at Airport road, but i think that is wrong. The needle starts wobbling once i get past 115 and I felt I accelerated even after the needle touched the 120 mark. I was running a GPS app in my iphone called MCN ride logger, and you won't believe it, it logged my top speed at 169kmph
I am sure the reading is wrong, I had kept the phone in my jeans pocket, maybe that's the problem. Planning to try putting it in the tank bag next time so that it gets a clear view of the sky.

The one thing I am the happiest is that now I can cruise at 90kmph in the highway and the engine does not feel stressed at all. In fact, 90 comes at less than 1/2 throttle now and the engine feels relaxed. This was my ultimate purpose for this whole exercise. (I wish I had an RPM meter in my bike )

More later.

Cheers,
Rishi
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Old 23rd September 2010, 16:14   #19
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what jet size are you running??
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Old 23rd September 2010, 18:19   #20
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Pilot jet: 27.5
Main jet: 120

Clip position of the needle is at mid-way now.
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Old 24th September 2010, 13:50   #21
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Originally Posted by jingaboysr View Post
Pilot jet: 27.5
Main jet: 120

Clip position of the needle is at mid-way now.
Hi could you tell the number of K&N you are using on your bike. Does your mechanic have any suggestions for jetting and K&N updates for a 350 ??
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Old 24th September 2010, 14:19   #22
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Default Bullet jetting specs

There seems to be a lot of question on jetting options for the Bullet, so here are Hitchocks recommendations.

S&B air cleaner jetting will be is similar to a K&N

Micarb are the same jets as the Mikuni spigot mount VM series

Enjoy
Attached Thumbnails
K&N and carb re-jetting for bullet 500 & 350. EDIT: Chart on pg 2-re-jetting0001.jpg  


Last edited by Rehaan : 24th September 2010 at 18:46. Reason: Thanks. Merged to a similar existing thread.
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Old 24th September 2010, 15:11   #23
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Originally Posted by jingaboysr View Post
Pilot jet: 27.5
Main jet: 120

Clip position of the needle is at mid-way now.
thanks mate. I am running 27.5 and 110 on my Std350 for an year now. The pickup has increased but the top end stays the same.
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Old 25th September 2010, 11:41   #24
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Quote:
Originally Posted by Hog Head View Post
There seems to be a lot of question on jetting options for the Bullet, so here are Hitchocks recommendations.

S&B air cleaner jetting will be is similar to a K&N

Micarb are the same jets as the Mikuni spigot mount VM series

Enjoy
Thanks for the chart mate, the exact values and positions can only be found out by a plug chop.

Can you tell me what are those needle jet positions O8, P0 and P2 mean?

@bradhey, I am using the model RC1060. I've also heard people suggesting RR1100, not sure what difference it would make.

@All, even though my in gear acceleration has improved, I feel a slight lag in gathering momentum if i whack open the throttle suddenly. Lets say i am going at 30 in 3rd gear and open up the throttle suddenly, I feel a lag. It feels like a clutch slip, the rpm goes up, without any significant increase in acceleration. I generally then reduce the throttle a bit and increase gradually, so that it feels like a smooth acceleration. Can this be because I am running rich somewhere or my clutch setup not being able to handle the power? I recently replaced the clutch plates with new ones and got the clutch assembly cleaned up with petrol. I have the 4 plate setup.

Also, what are the next set of non-invasive performance mods advised for a bullet?
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Old 25th September 2010, 11:47   #25
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Originally Posted by nickoo View Post
thanks mate. I am running 27.5 and 110 on my Std350 for an year now. The pickup has increased but the top end stays the same.
Hey buddy, where did you find the pilot 27.5? Please tell me, I have been looking for it all over Delhi, mostly in Karol Bagh & no success till now. And this search has been going for long. It would be great if you can help me with this.
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Old 25th September 2010, 12:01   #26
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I got it from Sandhya spares, JC Road, Bangalore.Had to search for half an hour in their stock of pilot jets and finally found some. There should be some more there, let me know if you need to get one.

i've read somewhere that Jayprasanth's friend now makes it at Pune. You can try that route also. But I haven't seen Jay around in the forum lately :(
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Old 25th September 2010, 12:04   #27
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Quote:
Originally Posted by jingaboysr View Post
I got it from Sandhya spares, JC Road, Bangalore.Had to search for half an hour in their stock of pilot jets and finally found some. There should be some more there, let me know if you need to get one.

i've read somewhere that Jayprasanth's friend now makes it at Pune. You can try that route also. But I haven't seen Jay around in the forum lately :(
Thanks man, it would be great. Let me just check it up with Nickoo who seems to be from Noida & in case I don't get any leads, maybe you can courier them to me.

As for Jay, yeah, even I haven't noticed him anywhere. The last I know, he was preparing for higher studies (abroad) & so may have left to some place. Not sure though. Do let me know if you hear from him.

Ride safe buddy, take care.

Regards,
Prakhar
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Old 25th September 2010, 12:18   #28
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Quote:
Originally Posted by jingaboysr View Post
Can you tell me what are those needle jet positions O8, P0 and P2 mean?
Those are different needle jets. Unfortunately not available in India.
But fret not carb can be set-up almost as good with what is available here and careful jetting.

Quote:
@bradhey, I am using the model RC1060. I've also heard people suggesting RR1100, not sure what difference it would make.
R1100 has larger filter area and it will make a nice change compared to 1060.

Quote:
even though my in gear acceleration has improved, I feel a slight lag in gathering momentum if i whack open the throttle suddenly. Lets say i am going at 30 in 3rd gear and open up the throttle suddenly, I feel a lag. It feels like a clutch slip, the rpm goes up, without any significant increase in acceleration. I generally then reduce the throttle a bit and increase gradually, so that it feels like a smooth acceleration. Can this be because I am running rich somewhere or my clutch setup not being able to handle the power? I recently replaced the clutch plates with new ones and got the clutch assembly cleaned up with petrol. I have the 4 plate setup.
It sounds like clutch slip and you should rectify it before proceeding else any kind of tuning would be wasted. Btw don't alter the jetting now, instead get the clutch corrected. Hope the cable is free and there is enough play? Is your clutch basket the one with holes or the plain non hole setup? If its the non hole basket, then moving to holed basket would yield better clutch performance. The holes makes it easier for the oil to drain out thus providing a quicker and efficient bite between the plates. Change the spring and change the metal plate if they're glazed and/or warped.

Last edited by Sankar : 25th September 2010 at 12:19.
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Old 26th September 2010, 19:05   #29
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Hey buddy, where did you find the pilot 27.5? Please tell me, I have been looking for it all over Delhi, mostly in Karol Bagh & no success till now. And this search has been going for long. It would be great if you can help me with this.
here you go. [FONT='Arial','sans-serif']Fuel Economy products ,New Delhi at 011-28759455,28758633. As far as i remember this shop is bang opposite the world famous in Delhi Joga Motors and has a big banyan tree in front of the shop. If the guy says that the jets are not avaialable tell him that Mr Navtej has send you. You'll get all the jets there.[/FONT]
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Old 26th September 2010, 20:40   #30
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^^ Thanks mate, next weekend I am on this. Will let you know what I get from there. Thanks again & take care buddy.

Ride safe.
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