Bonneville America Forums Forums Technical Forums Performance Mods Big Bore Kit

ok, ok,,,let me say and PLEASE inform me if you know otherwise ! After reading on the Big Bore for our bikes....it seems to me, even though the kits approaching 1000cc are more appealing to my base desires...the 904 kit is the most dependable if you are a daily rider type....which Bonnie and I fall into that category...so even though there is a part of me wanting the BIGGER Big Bore...the 904 seems to be the one to get ?????

I agree, best bang for the bucks.

yes best bang for the bike and has so far proven to be as reliable as stock. i have no regrets with mine

Frank

well , even though I'd like to have the "really big" big bore.......It sounds from general consensis that the 904 IS the way to go on my 790.....I can't find any real feedback on the "big ones" except for those that have beefed them up for racing....and then there is a question of longevity and practicality of operation.............oh well...sounds like a 904 for Christmas.

You won't be disappointed. The improvement from your 790 is far more in noticeable torque and power than 114 additional cc would lead you to believe.

My bike is more comparable in performance to a V-Twin 1200-1400cc bike.

904 is plenty of torque for two up riding, I barely got mine broke in before I went to Sturgis. I am about 220 myself, my girl and baggage put the load at about 400. I made some starts in second gear (accidentally) a few times from dead stops, and the mountains were no problem even when I was geared too high it pulled through without bogging down. Runs great as a solo, can keep up with almost anything now, and out run way more than before. I also did head work to mine, but for a start, the bore kit would be fine for more power.

RW.......What head work did you do ????????? and did you start with the old 790cc ?????

I had a 790, port polished the head +1mm oversize valves. Dyno coming soon, maybe this weekend

They work real good,Had the 790,got the 865 and a 904 the difference is like day and night and the 790 comes in second.

contact Matt (ditch_dr) he did my port/polish work. good price too

Has anyone done or heard of anyone who's done a 904 big bore using JE pistons kit? My local dealer has a mechanic that's Ducati and Triumph factory trained (read knowlegable) and they're trying to talk me out of the Wiseco kit. It's quite a bit more $$, due to the fact that there's no pressed-in sleeve. They bore out the head and Nikasil plate the cylinder wall, which is supposedly better? Better cooling? Any thoughts?

I'm not familiar with the JE kit. I had D&D (Pensacola, FL) do mine with the Wiseco pistons. D&D offers a higher compression piston instead of the Wiseco for the same price. I opted for the Wiseco. The first BB kits they did were with the Wiseco sleeves. They decided the bored and nikasil (like stock) was the better way to go. I don't know about the cooling, but it should last longer.

As Dave said above, you would have to put a LOT of miles on the bike to make a difference - you may never get there. I'm extremely happy with my bike now. Either way you go you will be very pleased with the BB result. I went for all the torque they could get especially in the middle range. That's why I opted to not go with the higher compression pistons. I wasn't just looking for maximum hp.

I even tried their lower mass flywheel but had them swap it back for stock. It increases hp at higher rpms but took away some of the torque at lower rpm when starting off. After all, we ride the bikes on the road, not on a race track. If you've got someone qualified to do the BB, do it. You'll never regret it and it's tremendous bang for the buck. My bike is staying the way it is as I have all the power I want even riding 2-up now.

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would you rally be unsatisfied if you only get 70,000 miles out of a big bore kit before you need to rebuild?

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I tried to explain to them that I'm not a "high-performance" kind of rider. Rarely do I get over 5000rpm. I don't doubt that JE makes good pistons, I'm just wondering if they're worth the extra cost. The dealership is scoffing at the Wiseco pistons, even going so far as to refer to them as "Cease-co". But everything I'm reading here sounds like they're reliable.

I should add that I meant the Wiseco pistons with the cast iron sleeves over the non sleeved with the Nikasil.

I've never heard of anyone saying bad things about the Wiseco pistons. They are probably better than the stock ones. How much better do they need to be? Tell them you want to do the BB to get more torque for everyday riding. I rarely go over 5000 as well.

Bob, this is but is Mary Esther near a Navy Helo training site called "Site 8" (I think). I trained there years ago and lived in Milton for a while. Nice area and I miss the low cost of living!

Pete, to get back on topic. Why not bring your bike down here for a vacation and get D&D to do the BB?

Yeah, I'm on the Santa Rosa Sound, East of Navarre, and South of Milton.

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Why not bring your bike down here for a vacation and get D&D to do the BB?

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I'd love to...

What would the total "out-the-door" $'s be at D and D (from your experience), so I can compare what my local stealership wants to charge.

just do the weisco 904, save some money, and enjoy the smile that gets put on your face. if it makes you feel better the big performance company for victories chose weisco pistons for his big bore kits and bill gately uses these sleeved kits in his race bikes. tons of guys with 904's and the only problems i have heard of are from improper machine work, installation, and break in. i did mine myself, beat the ****** out of the bike, and it runs better than ever

Frank

I have always sworn by Wiseco pistons, best out there in my opinion. I think the improvements come more from the increase in compression than the increase in displacement. the 904 is the easiest way to go requiring no machine work. I think one of the kits needs the cases hogged out for the larger dia. cyl. if I remember right and the other 2 are stroker kits requiring crank work.

All that being said, personally I'm sticking with my stock bore until I need a rebuild.

904 and 988 are stock bore, the 988 requires splitting the cases for a new crank. the 1100 is stock stroke but a big bore which requires the top cases to be bored. and the 1200 is the best of both worlds

Frank

Frank, just to clarify, IIRC neither kit is a "stock bore", however the cases don't need to be machined. The 989 requires a stroked crank, with stock rods.

I think Frank means the case is stock bore not the cyl.

if i were doing the big bore.. i would do the J&E pistons kit.. many of the racer's in the area.. all use J&E pistons...
Nikasil plate the cylinder wall.. yes much better...
and with the J&E piston you get a better piston...

Ed

tell you what, go here http://forums.delphiforums.com/acecafe/start then ask all the questions you want and be prepared to get more info than you ever could want. not the most huggable group of guys but if your serious about this stuff its a good place to learn something

Frank

Thanks for all the feedback guys. One shop I called wouldn't do it because he had no experience on Triumphs but based his experience he thought the Wiseco kit with the Nikasil plating without the sleeves would be the best (and least expensive) way to go. Now if I'd stop losing money in the stock market ( ) maybe I'll go ahead and "get 'er done".

biker knows absolutely nothing about motorsickles. I would never listen to him either. jeez. Tongueincheekofcourse When the real gearheads speak and I read the responses to their wisdom, i have to ask myself why is the question even asked?

hi pete ..here is some good reading on Nikasil plating ..

web page

and if you are doing this .. please make sure the rings you get with your Wiseco kit will work with Nikasil plating ???

i say go with the J&E because i know they make rings and Pistons just for this...

but it's your $$$$$$ so pay what you want it just seems that if you are putting out the bucks for the Nikasil plating you go the rest of the way also...

and from i was told..if you go with the J&E it will really be a 905 not a 904 so you will bigger

Ed

Stock rods with the 989 doesn't sound like a good idea.

Contact Jaymo54, he has them in his.

Who does cranks for the 988?

Here is one source, Bonneville Performance in Port Orange, FL: BP Engine Kits

I'm sure that others will provide additional sources.