22 Inch tires would increase the speed, if the speed sensor isn't located on the axle. I see that it has become a big enough issue, I would imagine that by the time I get mine, this I will just be able to throw money at it to get it faster without piping it. (I have begun to appreciate the stock exhaust sound, when on the trail)

But you make a good point with the magazine articles and feedback from test riders. We may have to actually jet these things for our altitude, and figure out what exactly the factory did to keep them from revvin out.

Has anyone hit the rev limiter in any gear? I would be interested to see if the limiter kicks in at the stated 9000RPM's. I decided to purchase the Yamaha Tach for mine, when I get it.

Keep up the great detective work Watson.....

 

So lets strap on 2 new warrior carbs and be done with it. Actually I cant afford the gas it burns already, so maybe just add some airflow with a K&N and try and optimise my jetting, I am not piping this thing for atleast 3 years. It takes that long for most companies to get their crap together and build something of quality. But another thought is changing spark plugs, It may be too cold, and I know most of you dont buy into the split fire thing But I have had very good results with them so long as you take care to make sure you are not going to go lean. I have had tremendous power gains on bottom and topend using them in two strokes, while not as dramatic i would suspect a possible small gain. Like I have told everyone before, Compression is where the HP is made if a wiseco becomes available with say 10.25:1 compression ratio I think you would see a good increase in power. The Yz 426 has 12.5:1 and runs on premium thats where all of its power is made and thats how it produces 50HP stock, FYI a DS has 9.6:1 so they could make more power that way. who knows? I intend to call up white bros soon enough and ask them what they think is UP?

 

Sounds to me like you guys have reached the top of the torque curve & it falls rather quickly after peak.

Just because an engine has a 9000 RPM rev limit, doesn't mean the engine will freely rev to that limit. I have driven many an engine that wouldn't achieve rev limiter even under a no load condition & even completely stop accelerating in first gear when this "artifical" limit was reached. If this is the case, running the Raptor downhill would have little, or no effect on top speed, due to the engine braking effect.

Lets look to the origins of the Raptor engine for an answer.

Essentially spec wise, the engine is the same (compression, cam (would be milder if anything), bore vs stroke, head design, etc) as the bike it came from.

In this bike, if memory serves me correctly, this engine was rev limited & designed to run out of power at approx 7000 RPM. This engine developed approx 49hp at the rear tire (I have seen dyno graphs, as well as specifications for this engine).

The reports so far indicate that the Raptor develops in the realm of 45hp at the rear tires, this indicates that the camshaft wasn't made "more wild" & and we know that the other specs are the same. Simple arithemtic dictates that if an engine develops torque at a higher RPM (which would be the case if the engine was cammed up for higher RPM use), more HP is achieved. This seems not to be the case with the Raptor, since peak HP is actually down a little from the bike. This all indicates to me that mid 7000s is as high as this engine will rev in stock configuration.

I belive that what we see here is that Yamaha realized that Bombardier was criticized for their low rev limit on the DS, but they also knew that with their current head, exhaust, cam, compression, etc, that the 660 wouldn't attain that RPM under normal operating conditions. So they put the rev limit at 9000, then they can advertise the fact, hence no criticism for the low limit.

Am I making sense here? Basically what I am trying to say is, if the Raptor engine made any appreciable torque at 8000 or 9000 RPM, it would be developing 55-65HP instead of 45.

Speed is a function of RPM vs gearing. I bet gearing it up would yield a higher top speed, I have no doubt it has enough torque in the lower revs to handle it. Gearing it down will lower top speed, as you would reach peak torque at a lower speed (just like what 4th gear is showing you).

 

86atc250r, I agree 100%.

I think it is misleading for Yamaha to claim that the Raptor revs to 9000RPM. That kinda implies that it would pull to over 8000RPM as shipped with stock gearing.

 

You guys with new Raptors must surely know by now that the two carbs on the Raptor are butterfly carbs and NOT roundslides--so a sticking roundslide carb is NOT the problem here. Check for a vacuum problem/leak in the supply to the second carb.

Flyin' Ryan

 

I have to agree with 86atc250r,

It sounds like the engine,exhaust,intake setup isn't making power over 7000 rpm or so. I would bet the limiter is at 9000 as yamaha states.

Still, this is better than the DS in that at least you don't have to buy a $300 rev box to get more rpms. Just make the other mods to get the power curve up.

 

The next time you are WOT in 5th gear, pull in the clutch. If the RPM's rise, there is no rev limiter(other that the 9,000). I also think that the motor just won't pull any more in the top gears. I haven't even seen one so I'm just supposing. I learned a long time ago to live by KISS(keep it simple, stupid). The easiest, simplest explanation is usually the correct one. We have some very good points in this thread that are worth exploring, but I just keep thinking that need to rule out simple explanation # 1 before you move on to more expensive and time consuming tests. In fact, just ride your new machine and let White Bros. or somebody else figure this stuff out.

 

Wait, there is something wrong here, no one has started putting down someone else's opinion.

 

I don't allow such foolishness in my threads. There are plenty of others for that.

<music from "The Good the Bad and the Ugly" playing>

...Our new Sheriff "Colonel" Sanders holsters his gleaming six pieces without having fired a shot, then polishes his new badge of justice and authority. The good local town folk, once distraught and despondent, whisper amongst one another, "Alas, there is finally peace in this unruly town!...."

Amen.

 

ridzhard,

Exactly...the simplest solution is usually the right one. Totally agree. My opinion...yes the Raptor has 9000 rev limit, but it doesnt reach it as is...."but" the limit is that high...so mod'ing it up will be beneficial without needing to worry until 9000 is reached. Thats good that we can do this with our mod's and know that they wont be snuffed out by a limiter over 7000 or so. Im planning basic mod's to increase Rpm's.

Question for you guys: If it isnt limited, other than the stated 9000, and the Raptor isnt reaching that.... what inevitably will result from dropping a tooth on the front, other than the obvious low end advantage? Since the limiter isnt being reached, will this mod (shorter sprocket on front) allow higher RPM's in top end than its currently reaching, thus maybe not affecting the top end speed as thought? Please add your comments...and remember...this is only assuming that it is "not" being limited to 7000 or so, but that it just isnt making those rpms up top. To avoid argument, please read the above thoroughly, as to not to confuse what Im saying. Thanks.

Great topic...lets keep it rolling in a positive manner.