What type of motor work for a hill-climber-CR 500

[rod248]

I have a stock '97 CR 500 that I use for hill climbing. I am looking to get more useable power out of it (mainly so I can run taller gearing). I run swing arm extensions with a rubber tire (IRC M5B) and also a Skat Trak Dominator paddle.

I would like to get a bit more grunt off the bottom end, and then the majority of the power on the top end.

Is porting the way to go? Milling the head? Reed cage spacer?

Any advice or experiences would be helpful.

Thanks,

Rod

 

[redrider30]

My brother won the AMA D23 600cc hillclimb title last year using the following combo on a '97 CR 500. Gorr ported cylinder, head milled .070, cases matched, Wiseco Pro-Lite piston, Moto Tassinari Delta V Force Reed valve, 46mm Lectron carb, Pro Circuit pipe & silencer and 15oz Moose flywheel weight. We prefer a Dunlop 752 tire mounted on a 3 1/2 in rear wheel.

This combo should allow you to use a 15/44-47 gearing combo on just about any type hill. Just a few suggestions. Good luck.

 

[EricGorr]

You guys racing hillclimb are a special breed, as if drag racing on flat ground isn't exciting enough you guys have to add G-forces :scream:

Forget about cooling systems and reliability, it takes pressure to get up that hill in a hurry. Rider skill is the big what if? When I talk to people before building a hill climb engine I always ask if they're building a dedicated bike or they plan to use it for multiple purposes. If its a dedicated bike I need to find out if the guy can keep it on the pipe, if the hill has jumps, what other stuff is bolted to the engine, and what fuel he can get a hold of.

The best engine profile is bore it to the maximum oversize, crank the compression to 9:1, and port the cylinder for a narrow rpm band that the rider's skill can maintain. Recently I built a couple of engines for a guy and his girlfriend who race hillclimb out East. He was an expert and she was a beginner. I built her bike with lots of low end so she could ride up the hill without flipping the bike. Because that would enable him to have a more enjoyable weekend. Remember that old saying "when mama happy everybody happy". I built his bike so it would blow up in 45 seconds of sustained running. Of course the hill is only 25 seconds which gives the engine an "oh Sh&t factor" of 2:1

Seriously, the CR500 was ported for an rpm range of 6,000-8,000 rpm with race gas oxygenated with MTBE (Philllips B32, Klotz Stealth, or VP C2), bored 2mm over within AMA rules, and a high compression ratio. The exhaust port was raised to 42mm from the top of the cylinder and the base was turned down 1.5mm so the piston was nearly kissing the head in thermodynamic terms.

So thasts my philosophy on hillclimbing, build a bomb and shoot up that hill without swallowing your tongue and you might win a few cheezy plastic trophies. ;)

 

[Lost]

Originally posted by EricGorr
You guys racing hillclimb are a special breed, as if drag racing on flat ground isn't exciting enough you guys have to add G-forces :scream:


So thasts my philosophy on hillclimbing, build a bomb and shoot up that hill without swallowing your tongue and you might win a few cheezy plastic trophies. ;)

OMG :eek:

I think ill stick to the occational hill climb on the trails i ride.. That's some crazy stuff!!!

 

[r_rider28]

I second redriders recomendations, and I'm glad to see Eric fully understands what it is we want. Good to know considering he has my cylinder right now. It's not the cheezy plastic trophy that makes it worth while, it's detonating the bomb and living to tell about that makes it real fun. RedRider is the current number 1 in district 23 600cc. I'm not sure but from the way his ride looked he may of swallowed his tongue.

 

[r_rider28]

I meant RedRider30 not just "RedRider" sorry Brent.

 

[jski]

If you don't mind me asking a question "How do you get enough fuel to feed the motor" I have a 1987 CR-500 motor that we put in a modified ATC chassis for sand hill racing. The thing is a rocket but we have went through 2 top ends in 20 runs from what looks like a lack of fuel. I'm running a 48mm carb and thinking a fuel pump might work but would like to know what you guys are running? Thanks

 

[r_rider28]

Sounds like a jetting issue. I have never heard of a problem in which enough fuel could not be delivered to the carb from the fuel tank. Are you burning methanol? If you are getting a steady stream of fuel to the carb then jetting is the only thing that could be wrong. Jet richer..

 

[hillclimber]

Eric

I was told that a CR500 will not rev past about 6200 RPM even with porting,pipe and carb work because the ignition starts advancing acting as a rev limiter do you know if there is any truth to this?

Brandon

 

[sharp7277]

hillclimber, thats a good question I was thinking the same thing but I didnt know the exact RPM. I noticed that when i drag race my CR 500 that if i rev it out too much it sounds like a rev limiter is kicking in. I dont beat my bike but I noticed it did this last weekend and I new it had done it before when I really got on it. What is with that? :confused:

 

[pursang262]

A PVL or Motoplat ignition will get rid of that pesky rev limiter.

1-440-988-4474

 

[hillclimber]

Can you explain a little on how them igntion systems work on the CR500 do they improve performance thrue the entire rev range or does it just keep it from advancing at higher rpm?
Thanks Brandon

 

[morph]

hey guys
i have the same ignition probs with mine so after talking to a few locals in the know i have bought a cr250 cdi.i run an 86 engine that has a ct racing drag port job 12.9:1 uncorrected comp and a 41mm PWK carb.this engine is in a 2001 CR500
my ignition is currently at a specialist on the other side of the country
having the curve's mapped before i run it on the dyno.i should have both maps in 2 weeks so i will post my findings.what the guy's here do is fit complete late model cr250 ignitions(cdi stator flywheel...$1300)to rev them to 9000rpm....big hp
i have also heard about 8000rpm is the piston speed limit before the piston ****s itself because of it's own weight????

 

[KiwiBird]

Morph, are you running a Wolf or something similar with dual curves?

Another trick is to try a closer clearance between the flywheel and trigger coil (one outside the flywheel) - .010" minimum.

 

[morph]

no just the stock cdi.wolf and vortex didn't want a bar of it any way due to it's age.to hard basket.
my mate runs a vortex on my old 2001 engine and i cant justify the $500
for what benifits it gives.i built mine as a flat out scary bike that has totaly different characteristics to a stoker that those systems are designed for
no doubt a custom cdi to suit my engine would unleash more hp but it would take more money/piston's/dyno runs that i cant justify on a bike that is too fast now.what i am looking for in the 250 cdi is the current perfomance but with more over rev just in case i need to hold a gear a bit longer and to get an impressive dyno chart to blow away people who think bolting on every go fast part available($$$) and falling short of my thought out set up that does't have any really expensive stuff on it.i'm still using the stock exhaust even.

 

[Shawn Mc]

Milling the head is going to get you your bottom end power. My CR was done at CT racing, and its a freakin brute. I used to use the bike as a general play bike and rode the dunes a lot on it. I had CT go through motor on the thing, and Alan went nuts. I had the FMF Fatty on it, but it literally blew up at the down turn. After putting the Pro Circuit pipe, its alot more docile. I dont really know how much he milled the head or raised the ex port, but it makes 235 bls on the compression gauge! Ya Race gas city. I was carrying 15/48 gearing without any problem at all in the dunes. Alan at CT said it was making 60+ hp without any problems. I believe him! I ended up buying a yz426 to ride moto on because Im well, just no man enough to ride that beast around an MX track. Im sure anyone is! :cool:

 

[morph]

i've got a CT RACING ported motor too.i got 56hp at the rear wheel@4800rpm
with all the stock gear bolted to it and lower comp due to the stock head volume and raised ex port.since the last dyno run i have raised the comp got a 41mm PWK and am waiting for my ignition to be sorted.trying to get it to 70hp@6500 .mine is to wild really it makes a stocky feel slow.great for the dunes though.hey shawn any chance finding out your specs as mine was an alcy drag motor before i got it.

 

[ceaser146]

Just replace the ignition system and wear a cup cuz that engine is gonno do like 12000 rpm tops

 

[morph]

i'm not following.
i'd be running for cover if someone got a cr500 to 12 grand

 

[ceaser146]

no you wouldn't you don't even hear the rpm change, the only way to know is to get a tach that hooks up to the spark plug and check that way, then you would run. but if you run with like 32:1 or 26:1 mixture you will be fine.

 

[morph]

i read some where any brand of CR500 piston has a limit
of about 8000rpm that the piston weight vs strength vs speed becomes a bit of a problem causing the pistons to come apart if over reved for to long.

 

[redrider30]

C,mon guys don't be such wussies, (jk) these things wont kill ya. Back to the subject at hand though. I have never heard a CR 500 hit any sort of rev limiter. My brother could rev his until it popped and never hear any sort of limiter like you do on a 250. I can also guarantee ya that its doin more than any 8,000 rpm. Likewise, my big Katoom also has no limiter, but I'm positive that it won't blow. Especially after the abuse it took last year.
Hillclimbing may be a strange sport to some of ya, but to us dedicated few who take it as seriously as RC does moto-x, it is extremely satisfying to say that I am literally "King of the Hill"

 

[redrider30]

Oh yeah, thanks for the props Robbie!

 

[r_rider28]

No Problem. All this talk about hill climbing and rev limiters. Got me amped up for round 2.