Factory b pipe manifold/headpipe I.d.
- Thread starter Vortex
- Start date
- Location
- Canberra, Australia.
Might be worth emailing Factory Pipe direct. They've always responded to my queries and should know EXACTLY when any changes in production occurred.
**This is from another thread but pretty interesting.**
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
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
Quinc
Buy a Superjet
- Location
- California