Bonneville America Forums Forums Technical Forums Performance Mods Why 904?

Sorry if this question has already been addressed, but why is the 904 Wiseco big bore kit the choice for most members? Does no one use the larger Bella Corsa kits, and if so why not? I can see why you might not want to go all the way up to the 1200cc, but what is the problem with the smaller ones like the 989 and 995?

From what i have seen just browsing the sites i think there is more head/machine work that has to be done for the larger kits where with the 904 you just have to have the sleaves installed, but i dunno...

The kits larger than 904 require more work. Need more time, tools, and knowledge it you want to do it yourself, $$$ if you have someone else do it. The 904 kit is simply re-sleeving the barrels. The kits larger than that are bore and stroke kits meaning re-sleeving the barrels and replacing the piston rods. Replacing the piston rods means that you have to open the engine case (beyond just removing the side covers) so this is a much more labor intensive project.

904 is largest on the stock barrels, the 989 is a stroked 904, lots of work and the crank is expensive, but the numbers it puts out is impressive. the 1100 requires new barrels, and the 12 is a stroked 11. the case also needs to be bored for the 11 and 1200 kits. lots of work, but a ton of power, and depending on how you look at it its cheaper then "upgrading" to a bigger bike especially if you like what you have

Frank

Thanks guys, I appreciate the thorough answers. So here is another question. Say I'm a college student that is interested in mechanics, where would I go to get some references on how to install those other kits?

Also why are the sleeves so important? Are they made of a stronger metal than the cylinder walls? Can you not just bore the cylinder walls without pressing in the sleeves? Sorry for all the questions. I've been reading through this forum for three years, but my understanding of this particular subject is so remedial that I haven't been able to find any direct answers.

The sleeves are a different material than the barrels. I don't think the aluminum (in our engines at least) is strong enough to withstand the friction of the pistons and rings cycling thousands of times a minute. The outer portion of our barrels are aluminum while the sleeves that the pistons go up and down in is a much harder material. Sleeves can be anything from cast iron, nickel ceramic coating (Nikasil), Electrofusion, and boron composite cylinders (I'm cheating by using some of the Wiseco materials I have on my desk right now). The barrels can only be machined so much to accommodate new sleeves because if you take too much out of it then the walls will be too thin and you risk blowing a hole in the engine where it is weakest. That's why the 1100 kits use a new, larger set of barrels. The sleeves are also removable by heating up the aluminum and pulling out the sleeve because the aluminum expands more than the other material. When pressing in a new sleeve it is frozen and placed into the heated barrels so that when the two pieces heat and cool each other they fit together very tightly. Then the top is machined smooth so that the mating surface is completely even to prevent combustion gasses from blowing out the head gasket.

Interesting. Can someone point me in the direction where I can find the 904 procedure, or post/pm the procedure itself? I'd like to see if I'm brave enough to possably do this myself later on or end up paying my local Triumph tech.

Big Bore how to!!!!!!!!!!!

Again thanks for your answers and patience

Caleb,
There is another way to go with the 904 Big Bore Kit.
D & D in Pensacola will sell you Bored Barrels and everything you need like gaskets in one kit for exchange of your barrels.

Click Here

Otherwise you will need to send yours off for machining and installation of the sleeves.

Carnold,
I have a guy here in Fort Worth that did the bore/sleeve work on my bike. He did a great job. I would give him a call if you are interested.

The Bore Man

the sleeves on the weisco kit are doctile iron, this is what the nascar guys use. for the bigger kits get in contact with bill gately as bonnevilleperformance.com as he is the guy who designed these. if your going with a 904 you have 2 choices, the weisco and the D&D kit. more guys have the weisco and have no problems

Frank

Isn't the D&D kit the Wiseco kit but with sleeves already installed to save the buyer the machine work? If so it should be as trouble free as the Wiseco direct kit except that the buyer can have the job done faster not having to wait on a machine shop.

That's what it looks like to me. Though you still have the added cost of shipping the barrels for the exchange.

No sleeves in the D&D. They are bored and nickle plated. From what i have been told by them(i have been in contact with them to have it done by them, can you say road trip from Pa-Florida). They say it is the same as factory just bored out. Must be pretty reliable i would have to think.

Nuthin,
H**l yeah I'm interested! Thanks!

what jack said, they use the weisco piston tho. you can also do an exchange with bill gately to make the 904 a weekend job.

Frank

I was out of town and late jumping in. I have the D&D kit on my bike. Their cost includes swapping your barrels for ones that have been bored and re-nickeled like your stock ones are. They use either the Wiseco pistons or their own custom higher compression ones. I went with the Wiseco. My number one goal was the most torque I could improve all through the middle to upper rpm range not just max. hp. It was everything I could have asked for.

The bike pulls like a much bigger bike and 2-up with the 18T sprocket is great. D&D used to do the full Wiseco with sleeves but now only do their non-sleeved version. They feel it is more reliable with a longer potential life. Based on the racing record and service skills they have, I have no trouble trusting their opinion.

I think the best way to answer the question on "why 904" is the way to go, just have a look at Bob's torque numbers in
in the dyno table



what else is there to say