The Twin Spark Psyched Bull !

ananthkamath · 2nd April 2007, 19:27

Is that a shorter header pipe or am I seeing things?

Sankar · 3rd April 2007, 13:03

Quote:

Originally Posted by ananthkamath

Is that a shorter header pipe or am I seeing things?

Yes, that's a shorter header. Temporary setup with stock muffler, will change over to a megaphone later.

The test run was satisfactory the torque is visible all over the powerband and pulling it means i can make the gearing taller. Another thing i noticed is that the i'm holding the handle steady but the bike's tail is going like a snake's tail at max velocity. Or more like the *** shakes you see in the hip-hop vidoes. The frame has to be trued, there's a slight bend in the downtube.

Apparently the 180 jet is a bit richer even with the needle at the leanest position so when i hold open the throttle at wot the bike flutters and when i close back the throttle the power picks up.

In the last pic Jk had posted you can see the head leaking after the ride. The acceleration was pretty strong initially, when the head was not leaking, and on the level ground i was leading jk for a while, but then later i lost the power a bit and on the downhill section he overtook me. But after that the power never came back like the first time.

With a foolproof head leak stopping technique, better manifold, better carburation and higher compression things could definitely improve.

srikanthgr1 · 7th September 2007, 14:03

Hi Guys
Nice Effort
But Did You change the timing and other CDI related things ??

Sankar · 26th May 2008, 10:22

Ahhh so long since the early days. Got a lot more to update regarding the Bull. She's running beautifully now. Done a recent Trivandrum Cochi trip on the Bull and the performance was too good, got a real nice fuel average too.

srijit · 29th May 2008, 20:39

Hi Sankar, please forgive my naive query, but why isnt there a decompression lever on your bike? Did your mods remove the need for one?

ps: that is one ripping sound your bike has

Sankar · 29th May 2008, 20:43

Srijit, the space usually reserved for the decompressor is now occupied by a second spark plug (bosch super 4). Hence there is no space for a decompressor and thus no decompressor lever either.

srijit · 30th May 2008, 09:59

So how do you get the engine to turn over? By kicking slowly/softly till the needle is in the green?
Or has that characteristic changed?

Sankar · 30th May 2008, 10:26

The only way to get it turn over is to kick it hard. If the Amp needle is in the centre then it will turn over without any major force on the kickstarter and it will start. If the ammeter needle is in the negative you have to kick it really hard to make it turn over and start.

When I had the valves and the seat redone last year the compression was so high that i could stand on the kicker when the ammeter was in negative. And the only way to decompress and thus start was to put the bike in 1st gear and slightly roll it backwards (sitting on the saddle). The bike would make a loud "phisssh" sound and the ammeter needle would be in the center.

The compression ratio is higher than a stock bull coz of the shaved head and the block. I tried running without a headgasket before on my old block and it was lapped to perfection, and it was partially succesful. But the compression was too high and eventually it self destructed. Now i'm using ultra thin custom copper headgasket, the advantage is that it doesnt leak and i can use layers which will help seal the combustion chamber perfectly and there won't be any compression leak. The only thing the copper gaskets seal is oil from the push rod tube and the outer part of the cylinder. In most std bullets the copper gasket seals the compression to an extent, which is okay with the normal compression but not with high compression.

And now the bike is running a revised cam timing. The effects are slightly lower initial pickup and really good top end. I have also added a megaphone exhaust (similar to the goldie pipe but not a goldie type), the megaphone does make it's presence felt and there sure is a gain. Does 80+ in second gear

This is waaay better than before.

spyking · 30th May 2008, 15:28

Hello!

What kind of Mileage do you get in the city/highway after all these mods?

-Ashwin

Sankar · 30th May 2008, 16:09

Quote:

Originally Posted by spyking

Hello!

What kind of Mileage do you get in the city/highway after all these mods?

-Ashwin

Thats the fun part!! I get around 26 to 27 if i rip on the highways. And generally inside the city i get around 30-32 as i don't get the chance to open up completely.

The highway figures i have quoted from my recent trip to Cochi.

This is due to the increased efficiency.

srijit · 30th May 2008, 17:11

He he, thanks for the info Sankar. Maybe next time I can take it for a spin...

pedrolourenco · 23rd April 2009, 17:07

Quote:

Originally Posted by Sankar

Srijit, the space usually reserved for the decompressor is now occupied by a second spark plug (bosch super 4). Hence there is no space for a decompressor and thus no decompressor lever either.

I saw a similar modification on one of the Enfield communities on Orkut. The guy had connected the decomp cable somewhere near the tappet cover. A similar arrangement is used in the AVL engine. Maybe you should try it out.

jkdas · 23rd April 2009, 20:12

Quote:

Originally Posted by pedrolourenco

I saw a similar modification on one of the Enfield communities on Orkut. The guy had connected the decomp cable somewhere near the tappet cover. A similar arrangement is used in the AVL engine. Maybe you should try it out.

What was the orkutian's name/id?

Sankar sold his bike and anyway, his bike didnt have a decomp lever.

pedrolourenco · 24th April 2009, 21:37

Quote:

Originally Posted by jkdas

What was the orkutian's name/id?

Sankar sold his bike and anyway, his bike didnt have a decomp lever.

It was quite a while ago. Let me search. Just wondering if I'm allowed to post the link here if I find it.

@jkdas
You can check these threads out
http://www.orkut.co.in/CommMsgs.aspx...4993&kw=Decomp

http://www.orkut.co.in/Album.aspx?ui...aid=1218440560

Someone has done a twinspark conversion with the decomp modification.

Mods please delete the next post.

__________________

pedrolourenco · 24th April 2009, 21:54

@jkdas
You can check these threads out
http://www.orkut.co.in/CommMsgs.aspx...4993&kw=Decomp

http://www.orkut.co.in/Album.aspx?ui...aid=1218440560

Someone has done a twinspark conversion with the decomp modification.

2nd April 2007, 19:27	#31
ananthkamath Senior - BHPian Join Date: Jul 2005 Location: Mangalore Posts: 1,209 Thanked: 80 Times View My Garage	Is that a shorter header pipe or am I seeing things?
	() Thanks

7th September 2007, 14:03	#33
srikanthgr1 Newbie Join Date: Oct 2006 Location: Bangalore Posts: 3 Thanked: Once	Hi Guys Nice Effort But Did You change the timing and other CDI related things ??
	() Thanks

26th May 2008, 10:22	#34
Sankar Senior - BHPian Join Date: May 2005 Location: Location Posts: 5,766 Thanked: 9,054 Times	Ahhh so long since the early days. Got a lot more to update regarding the Bull. She's running beautifully now. Done a recent Trivandrum Cochi trip on the Bull and the performance was too good, got a real nice fuel average too.
	() Thanks

29th May 2008, 20:39	#35
srijit BHPian Join Date: Jan 2008 Location: Trivandrum Posts: 598 Thanked: 8 Times	Hi Sankar, please forgive my naive query, but why isnt there a decompression lever on your bike? Did your mods remove the need for one? ps: that is one ripping sound your bike has
	() Thanks

29th May 2008, 20:43	#36
Sankar Senior - BHPian Join Date: May 2005 Location: Location Posts: 5,766 Thanked: 9,054 Times	Srijit, the space usually reserved for the decompressor is now occupied by a second spark plug (bosch super 4). Hence there is no space for a decompressor and thus no decompressor lever either.
	() Thanks

30th May 2008, 09:59	#37
srijit BHPian Join Date: Jan 2008 Location: Trivandrum Posts: 598 Thanked: 8 Times	So how do you get the engine to turn over? By kicking slowly/softly till the needle is in the green? Or has that characteristic changed?
	() Thanks

30th May 2008, 10:26	#38
Sankar Senior - BHPian Join Date: May 2005 Location: Location Posts: 5,766 Thanked: 9,054 Times	The only way to get it turn over is to kick it hard. If the Amp needle is in the centre then it will turn over without any major force on the kickstarter and it will start. If the ammeter needle is in the negative you have to kick it really hard to make it turn over and start. When I had the valves and the seat redone last year the compression was so high that i could stand on the kicker when the ammeter was in negative. And the only way to decompress and thus start was to put the bike in 1st gear and slightly roll it backwards (sitting on the saddle). The bike would make a loud "phisssh" sound and the ammeter needle would be in the center. The compression ratio is higher than a stock bull coz of the shaved head and the block. I tried running without a headgasket before on my old block and it was lapped to perfection, and it was partially succesful. But the compression was too high and eventually it self destructed. Now i'm using ultra thin custom copper headgasket, the advantage is that it doesnt leak and i can use layers which will help seal the combustion chamber perfectly and there won't be any compression leak. The only thing the copper gaskets seal is oil from the push rod tube and the outer part of the cylinder. In most std bullets the copper gasket seals the compression to an extent, which is okay with the normal compression but not with high compression. And now the bike is running a revised cam timing. The effects are slightly lower initial pickup and really good top end. I have also added a megaphone exhaust (similar to the goldie pipe but not a goldie type), the megaphone does make it's presence felt and there sure is a gain. Does 80+ in second gear This is waaay better than before.
	() Thanks

30th May 2008, 15:28	#39
spyking BHPian Join Date: Sep 2007 Location: Chennai Posts: 95 Thanked: 5 Times	Hello! What kind of Mileage do you get in the city/highway after all these mods? -Ashwin
	() Thanks

30th May 2008, 17:11	#41
srijit BHPian Join Date: Jan 2008 Location: Trivandrum Posts: 598 Thanked: 8 Times	He he, thanks for the info Sankar. Maybe next time I can take it for a spin...
	() Thanks

24th April 2009, 21:54	#45
pedrolourenco Senior - BHPian Join Date: Apr 2009 Location: Margao, Goa Posts: 1,268 Thanked: 1,527 Times View My Garage	@jkdas You can check these threads out http://www.orkut.co.in/CommMsgs.aspx...4993&kw=Decomp http://www.orkut.co.in/Album.aspx?ui...aid=1218440560 Someone has done a twinspark conversion with the decomp modification.
	() Thanks