Topic: Blackfin CB750 F1 BLASTER

[Retro Rocket]

Subscribed... Nice build...

[Blackfin5]

CB750R- There is a SOHC4 guy on ebay who made 100 sets and he seemed legit.  The SS lines are well crimped and correct length.  Just very stiff when installing.

[Blackfin5]

I took off the gpwerks pipes and may put them up for sale before ever turning over the engine.

Does anyone recognize these pipes now installed on the Blaster?

[Blackfin5]

There is a plate separator in the collector.  All stainless construction.


Reverse cone and mounted to a natural mounting point (passenge peg mount hole) on the 750 with no hanger needed. 


The angle of the rear pipe and cone match the natural angle of the frame and swingarm.


Easy access to oil filter.  The horizontal bar is just part of the jig.


So far, I love how they look and fit; but until the Blaster is fired up, I have no idea how they will sound.

I very, very much like the motogpwerks 4-2-1 pipes for the 750; however, there are a couple minor issues: (1) the mount location on the can, as discussed in this thread, it requires a custom hangar or bracket to be fabricated regardless of a K or F.  (2) the pipes do not exactly hug the underside of the frame and are directly under the oil drain plug.  It's impossible to change oil without leaking onto the pipes.  (3) the spigots going into the head are a bit undersized so it's difficult (for me at least) to get the copper gaskets to seal correctly.

This is not a sales plug and I am not involved with the manufacturing of these pipes except to offer up the Blaster as the template for the prototype.  I understand that the plan is for these pipes to be put into production very soon to bolt up on both K and F frames.  I am not yet at liberty to disclose the identity of these pipes, but will let you guys know as soon as I am able.

[SOHC4 Cafe Racer Fan]

There is a plate separator in the collector.  All stainless construction.


Reverse cone and mounted to a natural mounting point (passenge peg mount hole) on the 750 with no hanger needed. 


The angle of the rear pipe and cone match the natural angle of the frame and swingarm.


Easy access to oil filter.  The horizontal bar is just part of the jig.


So far, I love how they look and fit; but until the Blaster is fired up, I have no idea how they will sound.

I very, very much like the motogpwerks 4-2-1 pipes for the 750; however, there are a couple minor issues: (1) the mount location on the can, as discussed in this thread, it requires a custom hangar or bracket to be fabricated regardless of a K or F.  (2) the pipes do not exactly hug the underside of the frame and are directly under the oil drain plug.  It's impossible to change oil without leaking onto the pipes.  (3) the sigots going into the head are a bit undersized so it's difficult (for me at least) to get the copper gaskets to seal correctly.

This is not a sales plug and I am not involved with the manufacturing of these pipes except to offer up the Blaster as the template for the prototype.  I understand that the plan is for these pipes to be put into production very soon to bolt up on both K and F frames.  I am not yet at liberty to disclose the identity of these pipes, but will let you guys know as soon as I am able.

Very nice looking pipe, Kevin.

[brandEn]

Wow nice !

[Blackfin5]

Now if I can talk these guys into making pipes for our 550s! 

[Retro Rocket]

If you wish to sell the Motogp pipe i am very interested, i suppose it will all be down to shipping cost, but seeings though it breaks down so well it shouldn't be too bad. Your complaint about oil dripping onto the pipe due to the oil drain bolt position, why not take the springs off in front of the collector and move it out of the way...? I will be getting one of these pipes one way or the other but i will also be changing the last bend at the rear to make the muffler sit at a steeper angle ....

[Blackfin5]

Retro, send me a PM on the exhaust.  Yes, remove retainer springs and slide off pipe to change oil.  Just saying.....   It is fairly compact to pack and ship. 

[Retro Rocket]

Retro, send me a PM on the exhaust.  Yes, remove retainer springs and slide off pipe to change oil.  Just saying.....   It is fairly compact to pack and ship.

PM sent mate....

[Blackfin5]

Blaster back home with the welded up prototype in steel.  It should be replaced with production exhaust no. 1 in less than 2 weeks.  Will have the option of either stainless steel or black ceramic coated steel.  I was originally thinking SS, but I now am leaning toward the black pipes for the Blaster.

Here's an on the ground view of the pipes and the end of the cone/phone with a fluted radius.  No baffle inside.  No copper gaskets.  Cannot be fired up as it sits - so cannot comment on sound.  It's supposed to be a bit less tinney and more throaty, but not unbearably loud.

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[neevo]

Cool build. Thanks for sharing in great detail. That latest exhaust is very cool too, helps me out a bunch as I'm just about to kick start my custom header, secondary setup and it's nice to see such sweet lines.

Had a question about 4-1 vs 4-2-1, any reason why you mentioned the latter would be "smoother"?

[Blackfin5]

I don't know which is "smoother."  But I have always heard that in "theory," the 4-2-1 has more efficienct midrange performance and 4-1 usually moves the power band up and are more efficient in the higher RPM ranges.  It's much more complicated than this simplistic explanation.  The most efficient headers are the best scavengers; the ones which remove gas exhaust the best from the cylinders.  However dyno tests show that there really isn't that significant of a difference as "theory" suggests.  Dynos also show thete is not a materisl difference in the lower RPM ranges.  To me, 4-2-1 headers "feel" stronger for street use.  But hell, I'm far from an expert on these exhaust systems.  I just prefer a 4-2-1.  I have one on the Blaster but my 550s have 4-1 pipes.

[Parkwood60]

Cool pipe, I really like how tight it is to the bottom of the motor. The tightest I have seen previously is the vintage Bassani 4-1, but I have never been able to find one for a decent price. But that's not really a reverse cone at the end, its just a tapered end cap with a restriction in it. Its tapered on the outside, but not on the inside from the look of it.

That's gonna be loud. I made a reverse cone end or my megaphone on a CB750, but only left a 2" opening and its loud when wound out, but not bad at idle.

[Blackfin5]

Yes - not a true reverse cone.  As you say it's not tappered internally, only cosmetically. 

[Blackfin5]

If you look at the center hole that is the size it will be all the way through the cone once the baffle is installed. The exit at collector is 2 1/4" and the core will be 2 1/4" throgh the cone and to the endcap.

[Blackfin5]

Also.....the plate separator in the collector as originally designed was removed and these pipes were fabricated as a true 4-2-1.....

[neevo]

Cheers Blackfin, appreciate the clarification.

[albertaboy]

Im just tuning in. Nice build. I look forward to seeing the finished product. Cheers.

[Blackfin5]

Blaster gone for 2 weeks while production pipes and jig being made.  Next pic should.show new ceramic coated pipes.  There will be 2 disconnect points under the frame with retainer springs.

[Retro Rocket]

Blaster gone for 2 weeks while production pipes and jig being made.  Next pic should.show new ceramic coated pipes.  There will be 2 disconnect points under the frame with retainer springs.

Nice...

[KRONUS0100]

love them oil lines.  where did ya get em?

[Blackfin5]

Thx Matt.  See Reply #80 above pg. 4.

[Blackfin5]

Well, Phase 1 is essentially finished.  I just need to clean up the bird's nest in the headlight bucket to make room for the new headlight.  I have new LED turn signals wired up correctly now.  Of course, they do not flash - they stay on when switched.  So either I need in-line diodes or replace the thermal flasher relay with an electric one.  Which is the better way to go?

While waiting for the custom 4-2-1 pipes to be finished, I stuck back on the GPWerks exhaust so I can ride.  It runs a bit rough until warmed up.  So Blaster will get a tune-up - points, valve adjust, carbs cleaning (the float valves were sticking a bit) and synch, etc.  I haven't really pushed it yet, but it handles better than I anticipated on my mountain roads.  It's fairly "lively" and I like the feel of the 110/130 Bridgestones.  Not a "lean machine" like the 550, but no complaints.

Once I complete the 550 build, my plan is to pull the engine for a 836/Stage III balance/rebuild.







Seats which were awaiting install on some of the builds....

[Retro Rocket]

Gorgeous looking bike Blackfin, what color blue is that ..?