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Discussion Starter · #1 ·
A motor swap is what I really want but it seems almost impossible since there are no 900 motors for sale in where I live. Is a big bore kit going to give significant improvement or is it just gonna be a waste of funds? I'm talking about the DP kit by the way..
 
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Sell the bike, and go buy what you want. It will be cheaper, easer, better resale, and just a whole lot less hassle - Unless, your looking for a project, of which case - have fun.

A while back, a freind and I did a small block Chevy conversion on a pristine 1940 Chevy coupe. By the time we got through cutting the coupes frame, welding in a new subframe, replacing the rearend, wiring, exhaust, and making it all work, he had much more in it than if he had just gone out and bought what he wanted. However, him and I liked these types of projects, so it was a good weekend project.

Having pulled I don't know how many bike engines out and put them back in again after rebuilding; Unless you love projects, have a donnor bike to get the engine out of cheap, or love to wrench, my suggestion is sell what you have, and go buy what you want.

Brian F.
 

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Discussion Starter · #3 ·
Selling the bike and buying a bigger one was an option but not anymore, I have decided to keep it and swapped the forks etc. Put relatively lots of time and effort on it, it gives me what I need which is a lightweight compact machine. It lacks the power on the highway when we return home after a day in the twisties. The power is more than enough for me at the twists anyway, I am not capable of turning them with more than 100 mph :p What I am looking for is a bit of improvement in the max speed with maybe a marginal touch of low and mid speed acceleration development. I will not be doing the job myself but labor is pretty cheap here. What I need to know is... is it gonna be a totally worthless mod or is it gonna be beneficial for the money spent, which I will spend if the kit does not get bid above $1000. After that figure I am off the auction no matter what.
 

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It is not always the end goal that is what people want. I like the idea of the big bore kit. I know you could go out and buy an rs4r, but I am kinda like you I have lots of things done to my bike, I like it and I am proud of it. If you can get the kit for a fair price, I say go for it!!
 

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if you are gonna swap motor, why not a 4v?

big bore kits give you marginal power increases and may or may not kill the reliability of your machine.

for the $$$, I believe that a stock motor out of a bigger salvage bike is cheaper than a smaller motor that's being pushed to failure.


Q
 

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Discussion Starter · #6 ·
if you are gonna swap motor, why not a 4v?
I am not able to swap the motor cause M900 sales have been very limited here (so have been the bigger engined bikes for that matter) and it is almost impossible to find a motor off a salvage bike. Also, importing an engine is not a reasonable thing so swapping the motor is not an option.

big bore kits give you marginal power increases and may or may not kill the reliability of your machine.

for the $$$, I believe that a stock motor out of a bigger salvage bike is cheaper than a smaller motor that's being pushed to failure.
That's an interesting point and the kind of information that I am looking for. Thge kit is OEM, but it still is risky and may cause engine damage you reckon? If so I will not be doing it for an additional 12 hp (which the seller claims)
 

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Discussion Starter · #7 ·
Having done some search I guess the big bore piston kit will not deliver any significant performance without high compression pistons. The kit in question here is a catalog item, 96401898C. Comes with
big bore 680cc cylinders and pistons, variable-advanced control unit, set of carbon fiber lowered silencers, Dynojet carburation kit + DP filter and claims to increase hp by 12 figures. I am not sure where the HCR gets in the equation here, or what ratio these cylinders/pistons have. Any comments?
 

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Discussion Starter · #9 ·
Do you mean this kit
Yes. I asked the compression ratio and the answer is 12:1
 

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qfactor said:
...big bore kits give you marginal power increases and may or may not kill the reliability of your machine...
I'm not sure on the marginal part. I had a Hawk GT racebike, 647cc stock had 48hp. Wiseco 700cc pistons upped to 65hp, thats nearly a 40% increase which is pretty dramatic.

I did also add Carillo cromo rods, pod filters, and jetted the carbs, and premium fuel was a must. I do agree about reliability, mine would require new rings every year but that might not be the case on a streetbike.

A big plus is that you will learn a lot about engines in the process.
 

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I believe someone in Australia did a comparison between a 680cc & a 750cc engine. IIRC, the 680 kicked the 750's arse.

If it were my bike, I'd do it! (if the kit sells for the $ you're willing to spend.)
 

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Discussion Starter · #13 ·
Speeddog thanks for the link. Apparently it'll be worth it.
One thing though, are the certain specs mentioned in that article, such as:

"Cam Timing: Inlet Opens 31&Mac176;BTDC, Closes 88&Mac176;ABDC.
Exhaust Opens 72&Mac176;BBDC, Closes 46&Mac176; ATDC (CAM advanced an additional 3&Mac176;).
With Valve Clearance = 1mm"

results of the mod or necessary adjustments to be done with the mod? If this kit is not "plug and play" type and will need adjustments, I don't think I will be able to get those done...
 

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The timing advance should not be necessary. They did this to further improve performance.

Be careful with the DP kits like this though. If something breaks it wil be expensive and a PITA to replace.
 

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Discussion Starter · #15 ·
Be careful with the DP kits like this though. If something breaks it wil be expensive and a PITA to replace.
Can you elaborate please? Someone else said ealier that engine failure risk is involved with this mod.
 

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Well, the DP stuff is very expensive if purchased new. Lets say for instance that you break a ring and need to replace it you have to buy the full set of rings for both pistons and they are expensive.
If you can even get ahold of them where you are.

I am not saying the kits are unreliable as I have no first hand experience with them. The kit may last forever I don't know. I just know that locating replacement parts can be difficult and expensive.
 

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Hey there, I'm gonna say that if you want the extra power the engine swap is most definitely the way to go... If you want the power of a 900 engine then this 680 kit is not comparable. My friend bought and installed this kit on his 2000 m600 and it was nothing but trouble... His engine is "overstressed" as he likes to call it, and is breaking down all of the time... You also need to consider an oil cooler which can be big bucks to install but necessary to keep temperatures down with the added combustion.
 

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Discussion Starter · #19 ·
This started to sound a bit risky to me... I seriously wanted to do this mod but I don't want to risk the engine nor do I want to get an oil cooler. mywoody, what was the trouble your friend had because of this kit? "overstressed" as in "overheat" ?
 

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They mean that the engine's reliability to reproduce the same level of power isn't consistent due to the extra "stresses" applied on all components.

A better way to get to where you want to be is to sit down and make a "Design" plan.

1) how much power do you want? (60, 65, 80, 100 hp?)

2) how reliable do you want the bike to be? ( 200 mi/day, 200mi/week, 200 mi/month ?)

3) how hard is it to find replacement parts? no matter what it is, new or not, it will need to be replaced one day or another, for various reasons, it be human error (not obvisouly yours tho) or mechanical failure.


now research the cost of all the parts (including regular maintenace items for a year or so) for each options, figure out what you can and can't afford.

enjoy.

Q
 
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