SkiDaddy
Just Havin' Fun!
- Location
- Orange City, FL
What's the correct manifold ID for a 701? I did a quick search but didn't find it.....:frown:
B pipe manifold diameter
- Thread starter SkiDaddy
- Start date
'Crockett
Freelance Smartass
Reprint from a statement made regarding this subject by Group K on another forum . . . . .
Attn All FPP B-pipe owners
--------------------------------------------------------------------------------
During a battery of on-water testing with a FPP B-pipe equipped 701 Yamaha Raider, we encountered an on-going partial throttle detonation that we could not tune out. After a few weeks of trying everything imaginable, we started taking very close measurements of many component parts in search of a solution.
For comparison, we had another identical 701 Raider that ran perfectly … with no partial throttle detonation at all. After inspecting everything closely, we found that the diameter of the exhaust openings at the FPP manifold/head pipe joint was very different. The port diameters of our “detonation” Raider were about 1.650 (42mm) …. The same diameters on our trouble free Raider were about 1.850 (47mm).
After finding this variation, we contacted Factory Pipe about the different specs that we found. They confirmed that The B-Pipes from the early production years were originally manufactured with the smaller (42mm) port sizes. On-going development done by FPP technicians showed that increasing the diameter to 47mm resulted in better performance, and a greatly reduced detonation risk…. This was particularly important on engines bored larger than 701cc. So the B-Pipes made after that discovery were manufactured with the larger 47mm openings (don’t ask when that new process began because nobody remembers … and we “mean” nobody).
Sadly, these two diameters join together in a way that makes it impossible to see or confirm perfect diameter match-up between the two ports. Given this, we built template plates that would allow us to update the early B-Pipe parts to the new larger openings … and we could be certain that the two diameters would match perfectly when bolted together. Besides making sure that the diameters have identical centers, we blended the new diameters further down the port passages on each part. This blending requires some moderation, because too much grinding can break in to the water jacking of the head-pipe and manifold. It bears noting that we used the templates to properly enlarge the gasket as well.
We “updated” the diameters of the early B-Pipe on our “detonation” Raider, and were pleased to see that our partial throttle detonation had disappeared … and at the same time, we gained a bit of overall performance. With this experience behind us, we strongly recommend that “EVERY” B-Pipe owner check the exhaust manifold and head pipe inside-diameters. If they are the early 42mm version …. Updating them is a “ really good” idea…. Especially if you have a big bore. For owners who don’t want to take the time to make their own fixture plates, Group K will be doing the diameter update for $70 (gasket included).
Respectfully, Harry Klemm
__________________
Unless otherwise stated, responses to all forum posts are based on my personal experiences working within the PWC industry, and developing high performance PWCs since 1987.
www.groupk.com
I believe that the current FPP gaskets are all sized to fit the "new" stock FPP diameter manifold opening and can be use as a guide to port an early manifold . . . . . . I have done this several times. Remember, if you can't match the two perfectly it is better to leave the manifold slightly under sized from the head pipe I.D. so there is no lip facing the oncoming exhaust gasses.
Simply put . . it's always better to tumble over a lip into a slightly larger area than to "trip" over a ledge that's facing the flow.
.
Attn All FPP B-pipe owners
--------------------------------------------------------------------------------
During a battery of on-water testing with a FPP B-pipe equipped 701 Yamaha Raider, we encountered an on-going partial throttle detonation that we could not tune out. After a few weeks of trying everything imaginable, we started taking very close measurements of many component parts in search of a solution.
For comparison, we had another identical 701 Raider that ran perfectly … with no partial throttle detonation at all. After inspecting everything closely, we found that the diameter of the exhaust openings at the FPP manifold/head pipe joint was very different. The port diameters of our “detonation” Raider were about 1.650 (42mm) …. The same diameters on our trouble free Raider were about 1.850 (47mm).
After finding this variation, we contacted Factory Pipe about the different specs that we found. They confirmed that The B-Pipes from the early production years were originally manufactured with the smaller (42mm) port sizes. On-going development done by FPP technicians showed that increasing the diameter to 47mm resulted in better performance, and a greatly reduced detonation risk…. This was particularly important on engines bored larger than 701cc. So the B-Pipes made after that discovery were manufactured with the larger 47mm openings (don’t ask when that new process began because nobody remembers … and we “mean” nobody).
Sadly, these two diameters join together in a way that makes it impossible to see or confirm perfect diameter match-up between the two ports. Given this, we built template plates that would allow us to update the early B-Pipe parts to the new larger openings … and we could be certain that the two diameters would match perfectly when bolted together. Besides making sure that the diameters have identical centers, we blended the new diameters further down the port passages on each part. This blending requires some moderation, because too much grinding can break in to the water jacking of the head-pipe and manifold. It bears noting that we used the templates to properly enlarge the gasket as well.
We “updated” the diameters of the early B-Pipe on our “detonation” Raider, and were pleased to see that our partial throttle detonation had disappeared … and at the same time, we gained a bit of overall performance. With this experience behind us, we strongly recommend that “EVERY” B-Pipe owner check the exhaust manifold and head pipe inside-diameters. If they are the early 42mm version …. Updating them is a “ really good” idea…. Especially if you have a big bore. For owners who don’t want to take the time to make their own fixture plates, Group K will be doing the diameter update for $70 (gasket included).
Respectfully, Harry Klemm
__________________
Unless otherwise stated, responses to all forum posts are based on my personal experiences working within the PWC industry, and developing high performance PWCs since 1987.
www.groupk.com
I believe that the current FPP gaskets are all sized to fit the "new" stock FPP diameter manifold opening and can be use as a guide to port an early manifold . . . . . . I have done this several times. Remember, if you can't match the two perfectly it is better to leave the manifold slightly under sized from the head pipe I.D. so there is no lip facing the oncoming exhaust gasses.
Simply put . . it's always better to tumble over a lip into a slightly larger area than to "trip" over a ledge that's facing the flow.
.
Last edited:
SkiDaddy
Just Havin' Fun!
- Location
- Orange City, FL
BINGO! That's exactly what I was looking for.:arms: :arms: :arms: :arms: :arms:
Thanks to Chuck for pointing me in the right direction. :hail: :hail: :hail: I have one of the smaller manifolds & this is no doubt a contributor to my meltdowns.
Thanks to Chuck for pointing me in the right direction. :hail: :hail: :hail: I have one of the smaller manifolds & this is no doubt a contributor to my meltdowns.
SkiDaddy
Just Havin' Fun!
- Location
- Orange City, FL
Forgot to say - Thanks Crockett!:arms:
Idok
F1pro
- Location
- Nations oldest muthaF+++kin city
WaveDemon
Not Dead - Notable Member
- Location
- Hell, Florida
200 psi on a ported cylinder with pump gas? that's asking for problems.
SkiDaddy
Just Havin' Fun!
- Location
- Orange City, FL
It was only 190....:cool2:
WaveDemon
Not Dead - Notable Member
- Location
- Hell, Florida
more importaintly what size dome?
jetskier79
I'm goin' for two
- Location
- San Diego, CA
why is that more important?
Seriously, compression confuses. me. Static, dynamic, domes timing advance ahhhhhh.
I'm just running a blend.
Seriously, compression confuses. me. Static, dynamic, domes timing advance ahhhhhh.
I'm just running a blend.
Frosty
New York Crew
- Location
- Western New York
I just found out not long ago... pulled my pipe off and I have the old style. Mine is going out to Chucky tomorrow for head pipe porting and exhaust manifold boring...
I also heard that the smaller ID head pipe/manifold also robs your motor of some 5-7 hp... true or not :dunno:
jetskier79
I'm goin' for two
- Location
- San Diego, CA
or you could just be like me, and run whatever you've got, without really measuring anything.
Frosty
New York Crew
- Location
- Western New York
I'm down with that... when I get mine back I am going to etch 47 into mine, where the Factory B plate is. :biggthumpup:
FL-cracker
X-H2O
- Location
- old exit 72 Melbourne
Has anyone gone bigger then 47????? I went 48 with my manifold that was originaly a 42. I noticed a diffrence for sure! Who wouldnt want that easy extra 7hp??????? Even if you are surf only...your only robbing yourself! And who wants to scorch a piston?
Frosty
New York Crew
- Location
- Western New York
I wasn't sure how far you could go before getting into the water jacket... 48 eh? damn.
WaveDemon
Not Dead - Notable Member
- Location
- Hell, Florida
I belebe mine is 48 to match the size on my bigger intake.
Frosty
New York Crew
- Location
- Western New York
so let me ask you guys this: will i be able to notice the difference going from 42mm to 47mm on my ported 701?
WaveDemon
Not Dead - Notable Member
- Location
- Hell, Florida
FL-cracker
X-H2O
- Location
- old exit 72 Melbourne
48 with plenty to spare! I think some of these engine builders are holding back some info.:banghead: You could probably go over 50 if you wanted to....its just a matter of finding that sweet spot....Someone here most know the best diameter to bore to....come on its not gonna put anyone out of work:biggthumpup:
FL-cracker
X-H2O
- Location
- old exit 72 Melbourne
yes!:biggthumpup:
jetskier79
I'm goin' for two
- Location
- San Diego, CA
Don't I wish.....it's been mostly flat for months.
I'd care.....if my skis weren't already together. If it runs, I dont' touch it.