keen

K

keen

Member

Jun 17, 2003

21

0

• Jun 29, 2003

• #1

I purchased a poorly running 90' CR 500. The seller told me it would not idle and wouldn't rev. past 5K or so. In an atempt to throw parts @ the problem the seller replaced the carb, coil, stator and rebuilt the top end. After the purchase I checked the basics- air filter, silencer and pipe for clogging, carb cleaned/ stock jets/ float height etc., reed- no cracks, good seal, timing marks aligned, new plug. The bike was a bear to start and w/ the choke on it reved like the throttle was wide open... I said must need crank seals. The bike fired right up w/ the new seals. Went for a test ride 1) turning the idle speed up doesn't increase the idle it will die w/ the throttle closed 2) It doesn't like any load or it falls on its face- choke on or off. Plug is really dark. So I try the original carb- same problem. What next? it seems really rich but the carb is bone stock. Reeds??? Any help would save this bike from a cliff. Thanx

 

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tristan18au

Member

Jun 3, 2001

186

0

• Jun 30, 2003

• #2

a Crank seal or around that region

 

K

Kornholio

Member

Jul 11, 2001

24

0

• Jun 30, 2003

• #3

Seen as it is running rich I would check the reeds like you said

 

A

A-RustyDemon

~SPONSOR~

Dec 9, 2002

152

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• Jul 1, 2003

• #4

Also check the exhaust.. If it's been setting a critter could of made a nest inside. A friend had the same type trouble. Found a nest in the pipe packed so tight we had to cut it in two to remove it..:eek: Worked fine after that. Just a thought.. Good luck

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 1, 2003

• Thread starter
• #5

Exhaust is clear. I ordered a set of Boyesen reeds today. I believe it is rich but don't no why I would have to down jet it in order to run/ idle better on a stock bike.

 

D

dthoms

Member

Oct 6, 2002

175

0

• Jul 1, 2003

• #6

Keen,
Are you sure your adjusting the idle and not the air screw?, I some of the older Hondas the idle adjustment was built into the choke lever.
Who replaced your crank seals?
If the plug is dark, does it look like oil deposits on it?
I would check for a blockage, in the fuel line and pecock as well any obstruction in the air cleaner, boot and box. Also did some one punch this bike out and not have the cylinder relined? I saw a guy a couple of weeks ago with a CR 500 and he bored the cylinder and put in a over size piston without recoating the cylinder he made it about 5 miles into the woods before the piston lost compression and the bike quit.
How's the compression?
If you have enough compression, and enough gas and air.
I would then have the ignition system checked.
It seems awful funny that somebody would go the all of the trouble and expense of buying a new carb with out knowing that is what it is, I've never had to buy a new carb because it was worn out, nor do I know any one that has.
For the cost of a carb he could of taken it to someone that would of fixed it right the first time.
Keep looking sometimes trouble shooting is just a process of elimination.
Good Luck
DT

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 1, 2003

• Thread starter
• #7

The choke and idle speed adjustment are integrated. Idle speed doesn't increase fully open. The air screw has no affect either. I replaced both crank seals, crank bearings have no play. I have receipts for a complete top-end. Didn't perform a compression check but every kick lets you know it is tight. Petcock flows plenty of fuel in the bucket. I have gone over the basics. The new plug went dark really quick and the thing smokes (like fuel) even fully warmed. It has that muddy, not crisp feeling you have w/ a cold two stroke. I am going to try the reeds and hope that I don't have to try a CDI unit. I don't think ign. timing would cause a dark plug just a loss of power??? I am confused. Yes I was kind of suprised the orig. owner thru so many parts @ the bike, but I would hate to have to go to the shop w/ this bike too. Thanx

 

J

jmics19067

LIFETIME SPONSOR

Jan 22, 2002

2,097

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• Jul 2, 2003

• #8

it sounds like you have done quite a bit and this may sound silly but: fresh fuel mixed 32 to 1 with a bike specific premix oil?

If you suspect timing issues make sure the woodruff key for the flywheel isnt half sheared.

 

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overbore

Member

Dec 24, 2001

362

0

• Jul 2, 2003

• #9

I would make sure that it is working,as it wouldnt open the exhaust and
would show these same things.

 

R

Rcannon

~SPONSOR~

Nov 17, 2001

1,886

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• Jul 2, 2003

• #10

Based on the age of the bike, I think a person has to suspect the "rubber parts" Either crank seals or something in the carb.

I finally rode one of the CR 500's. It was a very cool bike. Do whatever needs to be done to make it work properly!

 

O

overbore

Member

Dec 24, 2001

362

0

• Jul 2, 2003

• #11

Just noticed the govenor part wasnt with my post before,but if it quit
working then it would not run right and maybe run real fast if it came
loose.hope this helps.
overbore

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 2, 2003

• Thread starter
• #12

Crank seals (L&R) were my first repair. I have gone thru both the new and orignal carb w/ carb cleaner and compressed air- each circuit air and fuel were open. I believe the eng. is rich not lean. Lean would be indicated by a cleaner plug and an increase in eng speed w/ the choke on. Based on the design of this carb the float level or a clogged air circuit could cause a rich fuel mixture- both are ok. Hopefully i'll see my reeds before the 4th. Thanx

 

L

Luft

Member

Dec 24, 2002

105

0

• Jul 2, 2003

• #13

I'd suspect the right side crank seal leaking and transmission fluid being burned in the ignition process.

 

4

490Dave

Member

Mar 18, 2003

316

0

• Jul 2, 2003

• #14

Im with jmics on this one too, maybe your 500 has a tendency to detonate giving it that "muddy" feeling. Try running a mix of premium pump and race gas.

Dave....

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 2, 2003

• Thread starter
• #15

I replaced the left side crank seal first. After I noticed the smoke in went a right side. I am running a 32:1 mix (premium w/ honda oil) I owned an 84' which had a detonation problem but this bike just plain runs crappy- no idle, falls on its face when you crack the throttle. I am an auto mechanic by trade. I have plenty of 4 cycle troublshooting experience. I completly understand two stroke operating principles but have limited real time troublshooting experince, save for odd balls like leaking crank seals or sheared woodruf keys on cranks and basic fuel system woes. A 2 stoke needs air, fuel and spark- the spark and fuel must be properly timed. The stator and CDI handle spark timing, the reeds/ ports control fuel tiiming. I keep going back to the basics but I still have a very poor running bike. Thanx

 

S

smarttoys

Sponsoring Member

Apr 29, 2001

199

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• Jul 2, 2003

• #16

I see that you said you ordered a new set of reeds. Did you remove your reeds and inspect them? A chipped, broken, or lifted reed will cause very poor running and usually runs like it's really rich. Do you have stock jetting in the stock carb? Did the bike just start running poorly all of a sudden when the previous owner had it or did he buy it like that?

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 2, 2003

• Thread starter
• #17

The reeds appear to be perfect and are perfectly seated. I even found a receipt for reeds but am going to replace them for testing purposes. The carb has the stock slow jet, needle/ position and main jet. The guy I bought it from never had it running right. He too purchased the bike and thought he could make an easy repair. Cosmetically the bike is really clean for a 90'-someone spent some $$$ on aftermarket plastic, chain & sprockets, skid plate, double wall bars etc.

 

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jmics19067

LIFETIME SPONSOR

Jan 22, 2002

2,097

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• Jul 3, 2003

• #18

Do you have a nice blue spark with a healthy crack to it when you kick it over? A yellow spark mightbe your problem. Have you done a ohm meter test on the stator windings and the ignition coil? wires hooked up nice and tight and properly? bad stop switch?

ALthough I have no idea what the timing curve is supposed to be you can hook up a timing light and see if you can spot something that just doesn't seem right to help narrow down a possible cdi problem. and that sounds like it is the only thing left but I hate taking a guess with money, and there is no real way you can check them at home.

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 3, 2003

• Thread starter
• #19

The spark is good as compared to most I have seen in the past. I did ohm check the new coil and stator- checked right on the money. It has a new kill switch. I cleaned and checked all coil/ stator/ CDI and kill switch wiring. I have a self powered MC timing light that I will use to check the timing after I install the new reeds. The problem w/ 2 stroke troublshooting is there isn't any advanced diagnostics- "check for spark @ the plug" how about measure the KV between 5-10 KV?. Timing- " make sure the timing marks align" how about @ idle 5 BTDC, 6K rpm 20 BTDC. They need real printed test routines instead of turning a lot of people into parts replacers.

 

J

jmics19067

LIFETIME SPONSOR

Jan 22, 2002

2,097

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• Jul 3, 2003

• #20

there is definately a way to check spark timing on a two stroke but it is different than most cars and I don't know it. I think it involves using a dial indicator or a degree wheel to put the piston at it's right spot and then you can rotate the stator plate to get a certain value from the trigger coil. something similar to timing the old air cooled VW bugs.

from what I have found with the ignition systems familiar in modern dirt bikes is that you really don't have to mess with the timing<unless you are trying to tune it beyond the way it sat in the showroom floor> beyond putting it together securely and properly. Theres is nothing mechanical to wear out and change like on a car except for maybe the magnet/woodruff key , only electrical/electronic parts to burn out and their mechanical mountings to break.

I kinda thinking that timing is not your problem after rereading all the posts. If the timing was close enough to start I would think that if it was too advanced it would be strong at idle and low revs<if you didnt break your foot trying to start it> or if it was retarded it would start to clear up a bit as the revs got higher.

if you have the reed block out lay the bike down on the ground and peer inside with the piston at top dead center. maybe <hopefully> just the bottom end of the cranckase is filled up with years of ancient oil/ gas that is making the bike run real ragged. Pull the plug ,flip the bike upside down put into gera and spin the rear tire to pump out the crud and see/ smell what was in there. if it is ancient gas in the bottom end you should be able to smell as soon as it comes out. right it all up ,button it all up , fire it up and try and keep it running till it clears out and then repack your silencer.

Just another freebie to try

 

4

490Dave

Member

Mar 18, 2003

316

0

• Jul 3, 2003

• #21

Originally posted by keen
A 2 stoke needs air, fuel and spark- the spark and fuel must be properly timed. The stator and CDI handle spark timing, the reeds/ ports control fuel tiiming. I keep going back to the basics but I still have a very poor running bike. Thanx

Click to expand...

In the origional post you said the previous owner put a new top end in it. im wondering if he got the right piston in there. ???

Just a thought....

Dave......

 

J

jmics19067

LIFETIME SPONSOR

Jan 22, 2002

2,097

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• Jul 3, 2003

• #22

good point Dave.

 

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DEANSFASTWAY

LIFETIME SPONSOR

May 16, 2002

1,192

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• Jul 5, 2003

• #23

Ive fixed a few 500s where they broke the piston and it got all wedged upunder the connecting rod and cracked the case. Maybe your bike previosly broke a piston or something and has a cracked case . Ive also seen the case center gaskets slip out and suck air or trans oil. Maybe you should get the motor pressure tested or vacuum tested for leaks.Its real easy to do on a 500 honda just go out buy a rubber frost plug for the exhaust and a steel frost plug for the intake and buy a tire valve stem assy at Pep Boys or Autozone or something. Plug the rubber one in the exhaust drill a hole on the steel plug and slip the tire valve stem through then clap that in the intake. With the spark plug installed take you bicycle pump and pump up the motor a little bit and listen for leaks or use soapy water around the gaskets and stuff. Dont pump too much only like 15 20 lbs.

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 5, 2003

• Thread starter
• #24

Put the new Boyesen Power reeds in today. Fired it up and it sounded ultra crisp, like a 2 stroke should :) Wheeled myself to my helmet and it dies :( played w/ plugs for 20 min. until I figured I ran out of gas.. duh. filled the tank and went for a test ride. SAME Problem! but in the process of running out of fuel I determined I am too rich. Problem is why would stock jetting be so far off? On a good running 2 stroke removing a little fuel can clean up some poor factory tuning but I think i'll need to do some big number jumps??? Thanx all

 

K

keen

Member

Jun 17, 2003

21

0

• Jul 5, 2003

• Thread starter
• #25

Went against the grain and down jetted went from a 55 piliot to a 48, top groove on needle from middle position, and from a 170 main to 165. Still no idle but now it will run thru the mid to top w/o falling on its face. Feels like a strong 250 not the 500 it is??? Thanx