Bonneville America Forums Forums Technical Forums Performance Mods Big Bore Questions

I am thinking about doing the big bore this winter and was comparing the options out there... I would like a comparison if the Weisco kit and the one South Bay has to offer.. I am leaning towards the one from South Bay simply because you dont ship anything out to be machined, pressed, etc.. You get everything you need in the kit... Also the South Bay kit runs at a higher compression ratio, 11.5/1 as compaired to 10.5/1 Anybody know anymore about these??? Would also even think about upgrading to the 988 kit that is offered since it comes with a pre prepped crank ( just turn in yours for core, like the juggs )

You might want to talk with the guys at Brirish Customs.

You don't need to send out your jugs to get machined, contact Bill Gately at bonnevilleperformance.com. He sent me everything I needed, and when I was done months later, I sent him my stock barrels back in the same container he sent me the already machined and sleeved barrels. As far as compression, I can't answer that, but if it gets cold where you are, you may have more problems on start-up cranking it. Either way, I think you'll be happy, I know I am.

my vote goes to the weisco kit. if you want to you can go with bill gatley and get everything to just install the kit, plus his cell phone for any issues to run into. thats worth is to me right there. the stroker kits are a lot of work and you need to know your stuff or know someone who is top notch. from what i understand 10.5 to 1 is about as high as you want to go on a carb air cooled bike so you dont get any ping or knocking issues with changes in quality of gas and things like that.

Frank

I had D&D (Pensacola, FL) do mine. I swapped barrels for ones they stock that are already bored and nikisil coated. For the same price I could have used Wiseco pistons (10.5) or go with D&D's higher compression ones (11.5). I opted to stick with the 10.5. My goal was to not give up ANY lower rpm torque for higher rpm hp.

I feel better about the 10.5 anyway. I burn Mid-grade with no problems and I now have 66 ft. lbs. of torque at 3400 that stays above 60 until 5250. I couldn't be happier and have no plans for more performance mods.

I also tried D&D's lower weight flywheel, but ended up having them swap it back for stock. It essentially gets you more hp, but I noticed a drop in torque starting off. It wasn't a trade off I wanted to make. The whole reason I did the BB was for more torque. I don't care too much about how much hp the bike has at 7500. I compare mine to similar bikes at 5250 where the torque and hp curves cross. Mine is right at 60. You'd be hard pressed to find a dyno of one better. I'm also using stock carbs and airbox.

Well, after talking to a few people today, I have to say, I am impressed with the Service manager and the price at D&D... Everything that the SBT kit has except for the HD clutch springs... ( 895, vs 1195 ) Kit comes ready to bolt in with rings already gapped etc..... Leaning more to the High compression kit.... What I got out of the conversation was they are getting the same or more torque from the high comp kit as the low, and a bit of a bump in HP.. As long as I dont mind running Premium fuel...
Mark

Mark, I assume you talked with Dink (Robert). He is the owner and service manager of D&D. They really know their stuff there. Many of their performance upgrades they developed trial and error with their Triumph racing bikes. Their racing team with Rob (his son) was in first place in the Thruxton Cup for two years. He's now racing a Triumph supported 675 and finished 7th running it the first time in Daytona this year.

Yup. That would be the guy.. Great wealth of knowledge... Especially from the racing standpoint...

So what kind of $ are you talking about? do the heads need to be cut to fit the bigger barrels?

heads dont need to be cut with any kits. with the larger kits the cases need to be bored out tho

Frank

My total cost with D&D doing all the install and 2 dyno runs was around $1250. last year. They sell the complete drop in kit (you swap in your barrels) for $895. You could do the work or have someone in your area do it.

Here's a link to D&D's performance parts:

D&D Performance

I have a reliable guy here, who did work on my VW motor.

It's up to you Mike, but I would want someone who had done the work before to do it. They would have a much better idea how things should be, etc. I wouldn't want to be a guinea pig even with a competent auto mechanic.

If you have the necessary wrenching skills (I don't) and want to do it yourself, that's different. Maybe some other guys here can give you their opinion.

Not to mention, a warranty claim would go down MUCH easier if only one source is involved. Their parts, put together by them, just about limits any argument over what went wrong.
Labor savings just ain't worth it. (in my humble opinion)