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Discussion Starter · #1 ·
Ok here is a topic that seems to be popping up more and more around here. I am looking at getting into my motor but do not necessarily want to go full blown big bore stroked build (or maybe I do). It looks like there are a couple of different options that seem to be the stages that people are going to. Assuming that the head is ported and +1 valves and all the goodies, dual exhaust, and megacycle or webb cam, the following seem to be the most popular options.

1. Stock stroke/bore with high compression piston. Looks like some guys are getting some very good numbers. I believe sparky is hovering just under 70 and looking for the last few hp.

2. Big bore (105 or 105.5) high compression piston with stock stroke.

3. Big bore, big stroke (+4,6,8) depending on your preference. (I would probably go +6). And high compression.

4. Stock bore, big stroke, not many people doing this I assume because if you get into the bottom end you might as well bore it.

Anyway we all hear about who likes their build but I am more interested on why I would not do 1,2,3,or 4.

I ride dunes, that is pretty much it. I love to race and hate to loose, also like hillshooting, and we spend most of the days just duning around.

If stock bore/stroke is getting near 70 hp is that build going to be too "wild" for lack of a better word to dune hard all day with?
What do you think is the best and least expensive way (all motor) to get 70 hp, or close. My concern is when we are spending thousands of dollars to gain a couple of ponies. If I am not going to install a stroked crank at the moment would I be better off just doing a stock stroke and bore? Also at what point is a new rod needed?

Lots of questions I know but I am thinking about all of this and I would guess there are many people out there that are doing the same "what to do next". Thanks and I look forward to a long thread with some great info for everyone.
 

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the stock bore build is probably the most cost effective...considering you don't have to bore or plate the cylinder. its 250 to go with the bore and recoat after spending 500 on a cam with springs 500 ond head work...and 800 on exhaust 260 on a controller 250 extra on the build shit doesn't look like too much considering the torque and maybe a couple extra HP
 

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std bore 12.5:1 je or a sparky special piston. web3 or cycle x2 cam, good port work, duel exhaust, oversized valves, springs, guides, pc3 and a oversized filter with box cut out. that should give you some awesome #'s and you will beat most guys on the hill. its not just peak hp you are looking for its tq combo. I went with a big bore after i dropped a guide and also added duel barkers. my hp started early and held for a long time on the dyno. Tq started around 4500 rpm's and climbed and held till 8000 to 8400 i think and when i ran the hill against a built ltr 450 i used to stay head to head with now i beat him by about 3 bikes. big diff in the big bore on the hidden power. question isnt just hp though its where the hp and the tq #'s start and where they end. If you have a motor that peaks at 68 hp but mostly carries at 60 to 62 then thats what you look at not the peak cuz your not going to run in the peak at all times. just my 2 cents.

Also remember that all the #'s posted i do believe are at sea level not adjusted for altitude. mine came in at 60 rwhp but that is adjusted for actual altitude. with my big bore i havn't got on a good dyno for a good tune yet so not sure what i am runnin now.



Capt
 

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Discussion Starter · #5 ·
Good info thanks. cost is not really an issue in reguards to the bore and plating like you said since it is only roughly $250 give or take. I have the pcIII barkers and prodesign already so that has been out of the way.
My only question as to wether to go big bore or not without going to a big stroke is more of a question of how much more work is it(like pulling the motor) to go big bore. Do you have to pull everything in order to just replace the stock piston with a high compression? Is it nearly the same to just pull it completely and bore and replate. I am going to do the work myself and have built motors for cars just have not done one on a bike. In a car it is much easier to just change out the pistons then to pull the whole motor to have the cylinders punched.
With that said if you tell me that the curve on a big bore high compression motor is quite a bit better than a stock bore high compression then I would not be opposed to just going for it all at the same time.
At some point I want to do a stroked crank big bore (assuming it is not bored already) so that is another consideration for not necessarily wanting to tear all the way down since I am planning on doing it this next winter.
 

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with the new rods on these stroker cranks you always have the option of using the piston you already obtain. So pretty much its what you want to do if you do the crank you have to split the whole case so thats something to think about top end is just the jugg.
 

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big bore or not u still have to pull the engine apart. go big and dont look back. Piston price is the same either way and you just pay for boreing and sleeve, i didnt go with a reseal i went with just steel sleeve. runs great.

Capt
 

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I agree, the only consideration IMO is the Money, the engine will produce more HP and TQ with a bigger bore and Higher compression piston, and of course a high quality head port and big cam will allow for the maximum flow. Just Do It !! and Hold on :thumbsup:
 

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Discussion Starter · #11 ·
Thanks for the info, kinda what I was thinking but wanted to see if my head was in the right direction from people that have done it and if they would have done it different.
Digital where did you get your engine work done? I think I read before you are from the Portland area right?
 

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Eugene Oregon, 120 miles south of Portland. I had the Yamaha shop in Florence (on the coast) tare it down and rebuild it. They used the Rocket Fact. kit that I bought. It went smooth, I had a small problem with getting it to idol, but the mechanic took it back down and reinspected everything and put it back together, now it flies like a run away train :thumbsup:
 
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