coffman vs. b pipe

[chriselmore_1]

i run the coffmans right that came with my old 650sn on my 61x and it hits hard!!! even with a chitty manifold port match job. i stuffed a seat from a 2.3 neadle and seat in the water line right before the stinger and went from a 120 to a 125 pilot jet and it hits even harder down low!

 

[masterblaster]

On my pipe i only run water to the headpipe with a jet in it. It got louder but totally worth the extra tug.

you must be riding this boat very slow in surf or you are getting water into the pipe through a screw you thought was closed,any other wise it would be to hot to touch and prolly melting stuff

 

[chriselmore_1]

no screws on the pipe . ive done the water splash after a good wot run and it doesnt boil off the stinger. i ride flat more than surf.
lake = 10 min drive
surf = 3 hour drive

 

[Liquid Graffix]

Anyone ever try the ghetto b pipe - running an extended cone Kawi 650 pipe?

 

[motoman96]

i ran a sizzler on my fx1 last season. worked great, i now have a b-pipe so I will see what the rave is all about with the b-pipe. The sizzler is in-destructible tho.

 

[FolsomShredder]

I want to dry out my coffman but Im scared!

 

[brett]

just run it.

 

[tnj4life]

I want to dry out my coffman but Im scared!

Go to home depot in the hardware section where all the nuts and bolts are, look through the bins till you see the nylon spacers. Theres one thats 3/8s in diameter different lenths. You get 2 for around .70 cents. Throw one of those in where your hose runs to the stinger. Its a hair more than 4 millimeter so you shouldnt have any issues. Dont be scared my friend.

 

[chrisdoc0608]

I run a Coffman pipe on a 62t/61x w/ tl and it rips

 

[blitz]

I was running a coffman lighting pipe last summer and up grated to a b-pipe right before going to Daytona and was not impressed. The coffman had more bottom end hit. If any one is interested its for sale. The pipe is pictured in my avatar.

 

[chriselmore_1]

so i talked to art at jetworks today about getting my porting done and he told me he used to take the lower barbed fitting off the head pipe and restrict it just like the lower b pipe screw would do. he said its a great pipe but the b pipe will let the rpms get slightly higher.

 

[Ochocoronas]

Go to home depot in the hardware section where all the nuts and bolts are, look through the bins till you see the nylon spacers. Theres one thats 3/8s in diameter different lenths. You get 2 for around .70 cents. Throw one of those in where your hose runs to the stinger. Its a hair more than 4 millimeter so you shouldnt have any issues. Dont be scared my friend.

What do you think about running a 2.0 needle and seat?

 

[Quinc]

I run a seat drilled out to 2mm.

 

[bored&stroked]

Holy old posts

 

[kevbo]

Sizzlers havnt been made since 1994.

 

[TheBuzzard]

The coffman creates just as much power as the b pipe. I haven't done back to back but it's all about the porting. Ported cyl rips with either pipe. I've got a couple coffman head pipes modded by factory X racing. Has a screw in back to restrict water dumped in the chamber

 

[kevbo]

I can usually bypass enough to get the temp up. Sometimes I have to fill Coffmans hole and drill a smaller one. The Sizzler is shorter and has steeper cones than their Kawasaki version. It works as well as any wet pipe on small engines.

 

[theVetteman3]

Great old thread with some good info. I recently got a Sizzler and put it on my 650 wave jammer. Labor Day weekend we data logged the heck out of the ski, 48.5mph at 7060-7080 rpm. I have a ball valve cutting the water line to the stinger down to half, as well as a flow control valve. Based on feedback here I am definitely going to try cutting the water down more to the stinger and possibly head pipe. This pipe has one ring cut which supposedly adds proportionately more rpm vs low end lost. Apparently a popular racers mod from back in the day.

I used to have a cheater pipe set up on the same ski. Previous max was 47.8 under perfect conditions. My best data logged run was 44.6 and 6600 rpm. For those interested how they compare, the cheater pipe was a good upgrade from the stock muffler exhaust, but the Coffmans is a much beefier, 5" dia big pipe. It hit much harder than the cheater pipe, and over a much more discernible rpm range. The power hits like a light switch, which I really like. The cheater pipe is a good baby pipe. The Coffmans is much closer to what a FP can do. I can't tell exactly because I haven't been on a ski which has run both. This is just based on feel being on other yamahas with FPs.

Anyone know what rpm these pipes make peak power at? I'm right at my 701 limiter now, which I'm sure is way above what they were designed for on 650s or even 701s.

 

[kevbo]

Most Yamaha 650 pipes were shorter because of the low port height. I found my full length Sizzler to hit a wall around 6950 rpm. This is on a 61x cylinder with an 81mm bore and 182 degrees open exhaust. My full length Kawasaki 650 Coffmans hits the wall at 6700 rpm with the same exhaust timing. Im about to do a 701 and 144 pump swap in a Jammer. I may end up using a Kawi pump if the 144 is too much work.

 

[theVetteman3]

Most Yamaha 650 pipes were shorter because of the low port height. I found my full length Sizzler to hit a wall around 6950 rpm. This is on a 61x cylinder with an 81mm bore and 182 degrees open exhaust. My full length Kawasaki 650 Coffmans hits the wall at 6700 rpm with the same exhaust timing. Im about to do a 701 and 144 pump swap in a Jammer. I may end up using a Kawi pump if the 144 is too much work.

@kevbo that's some good info. You mean shorter pipe was better suited to the yamaha 650 because it helped gain rpm? All else equal a shorter pipe will give you higher peak power and rpm, as you saw on the engines with the same port timing. Thanks for the rpm on those, that is interesting.

Feel free to drop me a line when you start working on the jammer. I am the godfather of sorts with jammer engine swaps, with a pwctoday build that started in 2012. Not the first but definitely the one who has posted up the most useful info for others. I havent done a pump swap but I have been involved as a consultant on a few from the larger wave jammer Facebook group. So far a friend in Canada has apparently got his up to 53.9mph with a 701 dual carb and 155 pump. After doing lots of pump swap work on my 550/800 I just want to see how far I can push the stock pump on this ski. So far no complaints. It hits hard and goes way faster than any yamaha 650 has a right to.