Translation please!

[cajun]

Okay here is the setup for the story. I am going to have a 680 big bore installed on my XR650R. I posted here and several other places for advice on who to use.

One of the suggestions I got was from Precision Concepts. I'm going to paste my email to them on here and then their first response and then there second response. Would someone please help me figure out what they are saying and what I shoudl do?

(My email to them)

I have a 2001 XR650R that I would like to consider putting a 680 big bore kit in. I use it for off-road desert riding, woods tight trail, and I also have it converted to SM and use it on road only, no track.

I would like to consider having someone like you install big bore kit and other parts to maximize HP while still maintaining as much reliability as possible. I have it fully uncorked, FMF header and White muffler, and Edelbrock carb. I will probably have the Edelbrock bored.

Would you please let me know what you would recommend to fit my purpose and the parts and cost for you to install? I will ship the motor.

Thank you,

(Their 1st response)

Hi Jim,

I'm a bit confused, do you use this bike for offroad or SM?

Diane

(Their 2nd response)

For offroad, we found that while the bike felt faster, it was not and was more cumbersome to turn with the big bore in.

Honestly can someone tell me if this is serious and I just dont' get it or what?

[weskc35k]

Her first response i understand as i didn't at first get what you where saying but i do now.

Mate sometimes they are talking about the crank effect,it's like why a 125 turns better than a 500 sorta.

Talk to bwb663 i think is his handle he has done all the mods you are talking about and knows guys with other set-ups that may work as well.

[cajun]

Her first response i understand as i didn't at first get what you where saying but i do now.

Mate sometimes they are talking about the crank effect,it's like why a 125 turns better than a 500 sorta.

Talk to bwb663 i think is his handle he has done all the mods you are talking about and knows guys with other set-ups that may work as well.

I have been talking with BWB quite a bit and he's never said anything like this.

The biggest reason a 125 would turn better than a 500 is because it's smaller and lighter. The more I think about it I'm thinking this person doesnt't have a clue what they're talking about. Or I just don't understand them.

[Garth Knight]

Reading between the lines.

I think they are trying to tell you that the 650r already has more than enough power for off road, and you would be better to save your money,also if it did make more power (big bore) you wouldn't be able to use it much (how often throttle wide open on bigbore 650r in woods tight trail)?

You asked for their recommendation, you got it (dont bother with the bigbore)

[BWB63]

It is simple to under stand! Once you go to 680cc you will be pulling 10 extra horses! That is a lot of weight and can slow you down quite a bit. Maybe she is blond? Stock uncorked = 44rwhp/55bhp, header/muffler/carb = 48rwhp/59bhp, 680cc with all the extra's = 58rwhp/72bhp. My XR680cc bike won everything at the sand drags......yes, everything. The trick banshee's running alcohol would get me off the line, the North star buggies looked a lot faster but, Second was a CR500 on nitrous. I think if the guy on the CR500 would have gone with less paddles, stock swing arm (his is extended), weighed less and was able to control the bike (he had a hard time getting the nitrous back on after the shift) he would have taken me. All the stock engine XR650R's didn't stand a chance. So, as for the engine reving slower making the bike slower; I didn't see it. Now for top speed? I couldn't get much more then 102mph with 48rwhp. I am getting 118 with 15/47 gearing now at 58rwhp. I don't think I could pull that with a stock bike. I think the bike might rev slower with the heavier weisco piston but, it developes much more torque sooner to make up for it. I think that equels more traction for the added horsepower. If you are insane and want it to rev quicker, lighten the flywheel 12~16oz.

Here is Lewis' CR500 Nitrous bike:

I whish I would have snapped a shot of the bottle under the rear fender, maybe next time. He couldn't take me at the dry lake bed either. He is pulling more horsepower then I am so that is why I won. Like I said, all that extra horse wieght really slows him down. (At least the beer belly is:bonk: )

[pburke]

Is the big bore kit useful if you had in mind to run the Baja 1000? Just wondering where to put my upgrade dollars. Bike seems a bit weak to me without any power mods (just have Edelbrock and FMF pipe on it right now)

I don't plan on winning the race - just finish, so reliability comes first for me.

My plan was to perhaps get a mild cam upgrade, open up the side panel and swap the exhaust for a White Bros E series pro meg with White Bros. headers. going 680 sounds like a lot of work for not really a major gain that's going to show results short of wide open running.

[BajaBoundMoto]

Don't go with the 680 IMO.

For part of what "cajun" sounds like he wants, "woods tight trail", it's going to be more difficult to ride. Depending on what he means by "desert off road" then it may or may not be better. More fun and exhilarating possibly but more difficult to ride and not as fast of a finisher.

The effects of the big motor can be felt in the the way the bike turns & flattracks corners, in the rough/tight, etc... (all negitive ways imo) That's what Diane was meaning.

And for "pburke" considering a 680 for the Baja 1000, don't do it, leave it stock. Matter of fact don't even do the cut out side panel. Why change more air filters during the 1000 for a slight increase? Why give the bike a chance to more easily suck water in deep crossings?

I've ridden/raced plenty of 650Rs in Baja, stock motors and not. For this past 1000 we ran a cam and cut airbox. "Surfnride" and I split the 2nd half of the race and we aggreed we'd rather have had a stock cam and solid side panel. The bike would have been easier to ride in the rougher sections and we had a lot of silt. But for the upper 1/2 sections the riders probably liked the motor.

For the sand drags or super moto, sure, go ahead and do a big motor if ya want (i don't know anything about those sorta things).

[cajun]

Okay I didn't go into all the details of my riding conditions and didn't think I need ed to. I probably ride tight trials 5% (I also have an XR400R). I do ride desert in Big Bend TX and that is my favorite riding, we will cover over 300 miles in an 8 hr. day some technical some fast. I do also use the bike to ride around town (Houston) and commute to and from work when I just need some joy. I have probably put 5000 miles on the bike in the past two years on pavement (SM setup) and freeways the other 4000 dualsporting. All of my riding is purely for fun no racing. But I love speed and power.

I never thought of the fact that adding almost 10 horses would amount to so much additional weight. Maybe I should shed a few pounds. Thanks BWB!

[trailsurfer]

Listen to Baja Bound, don't ruin your bike. The fast guys don't jack around with that crap.

[pburke]

And for "pburke" considering a 680 for the Baja 1000, don't do it, leave it stock. Matter of fact don't even do the cut out side panel. Why change more air filters during the 1000 for a slight increase? Why give the bike a chance to more easily suck water in deep crossings?

I was thinking that those issues would outweigh the power increase. I'll probably stick with suspension optimization and more practice, which seem to be the key elements to making it to the finish. Also saves $$$$ for decent lights, etc.

[weskc35k]

Cajun most mx'ers 125 and 250 share the same frame and the smaller capacity allways turns better because of less gyroscopic mass it's just physics not beliefs,however a 680 i believe should turn so similar to a 650 that you could not tell the difference as the difference in piston weight would be FA.

I may not be right that is why i said check with BWB63 as he knows a lot about the 650.

Anyway there is no replacement for displacement.

[BWB63]

I never thought of the fact that adding almost 10 horses would amount to so much additional weight. Maybe I should shed a few pounds. Thanks BWB!

I think it depends on the size of the horses. If they are just quick little ponies then they won't weigh as much as big fat slow horses. 10 big fat horses is a lot to pull, and you would need a horse trailer to pull them in (a big one for 10 horse) and that weighs a lot also. Then the hitch on the back of the bike (heck how do you mount a fifth wheel on a bike?) is heavy also.

P.S.

There are those that have raced or ridden the 650 & 680cc to it's limits and don't like 680cc for what they do. Listen to them. There are those that have done the same and love the 680cc for the samething and other things, listen to them also. The bikes can be setup different, power delivery could be different weight of rider, riding style, ability but, you get a better idea of what you are getting yourself into if you go 680cc. I always get a kick out of those that are not much more then uncorked, haven't ever push the limits and will tell you, don't get the Edelbrock it isn't worth the money, stock exhaust is just as good as anything else out there, 680cc is a waist of time and will make you engine less reliable, Honda biult it this way why would you want to change it?.......and they have no clue. A 680cc engine that is biult right is more reliable then a stock bike if they are both ridden the same. There is no doubt about that. The problem comes in when you are now riding the bike at a much higher level more often. The S/S valves will last much longer then the stock intake, the corrillo rod is much stronger with better bearings then stock, stronger timing chain and what ever else you want better/stonger. I don't go over rev on the ignition, that is looking for a shorter life but, if that is what you want/need then you are willing to pay and rebiuld sooner.

[hill5150]

How the hell does a 680 motor rebuild add weight to a bike. Enlighten us.Please.....

[BWB63]

How the hell does a 680 motor rebuild add weight to a bike. Enlighten us.Please.....

I think it was a joke........ "adding ten more horses" ?

[hill5150]

I think it was a joke........ "adding ten more horses"

got it.......?

[cajun]

I hope everybody else got it.?