CR500 1985 impressions

[Old Geezer]

I agree. Idle is probably too low. I'm not leaning it out. It will idle when warm, but seems low.
I'll play with the idle screw setting. Is the pilot circuit a possible issue here as well?
Thanks.

Yep. I would start with setting the idle a bit higher and see if that does the trick. Otherwise, your pilot jet may be too small (lean). Try driving along at 1/8 throttle for a spell, then pull in the clutch and hit the kill switch to coast to a stop. Check the color of the plug; it should tell you how the pilot circuit is functioning.

 

[everfree]

Yep. I would start with setting the idle a bit higher and see if that does the trick. Otherwise, your pilot jet may be too small (lean). Try driving along at 1/8 throttle for a spell, then pull in the clutch and hit the kill switch to coast to a stop. Check the color of the plug; it should tell you how the pilot circuit is functioning.

Great, I'll give it a try. Thanks for the tip.
I always start with a clean plug. But when I pull the plug, it has a wet, black look, so I know things are not quite right.

 

[Old Geezer]

Great, I'll give it a try. Thanks for the tip.
I always start with a clean plug. But when I pull the plug, it has a wet, black look, so I know things are not quite right.

It's certainly possible your pilot circuit is way too rich and is basically flooding the plug when you're coasting off the throttle. We all know that these Husky's are pretty rich down low, so perhaps that's your issue vs. being too lean. It becomes trial and error eventually. Your plug is telling you something. By running steady at 1/8 to 1/4 throttle, you should be using just the pilot circuit. You can do a similar test at 3/4 throttle (checking the jet needle/needle jet combo), and at full throttle (checking the main jet) - run it there, pull in the clutch and hit the kill switch and coast to a stop. All this assuming you have a Mikuni carb. That isolates the various fuel circuits and the plug will tell you how she's burning. Sounds simple, but reading plugs isn't as simple as one would hope.

 

[everfree]

It's certainly possible your pilot circuit is way too rich and is basically flooding the plug when you're coasting off the throttle. We all know that these Husky's are pretty rich down low, so perhaps that's your issue vs. being too lean. It becomes trial and error eventually. Your plug is telling you something. By running steady at 1/8 to 1/4 throttle, you should be using just the pilot circuit. You can do a similar test at 3/4 throttle (checking the jet needle/needle jet combo), and at full throttle (checking the main jet) - run it there, pull in the clutch and hit the kill switch and coast to a stop. All this assuming you have a Mikuni carb. That isolates the various fuel circuits and the plug will tell you how she's burning. Sounds simple, but reading plugs isn't as simple as one would hope.

That sounds like a good plan.


Yes, I've got the 38mm Mikuni carb. I'm riding at 1,500 - 2,500 ft. Running a premix of 50 to 1. (Golden Spectro)
At that premix, I think I'm running a little too rich on the main jet, causing the plug to foul enough to be less than ideal. Combined with a low idle screw. The previous owner was probably running a different premix and had it jetted for that premix. More oil, less gas - leaner.

 

[Old Geezer]

Although all the jets work in concert with each other across the full spectrum, the main jet will have very little to do with your down-low pilot mixture, just as the pilot jet will have very little to do with full-tilt-boogie main jet operation. And since that's where you seem to have the issue (hell, it could be something entirely different going on, but one must start somewhere) I think I would mess with the pilot jet first, then proceed to tune the jet needle/needle jet/main jet - in that sequence.

You may be right, though, if running too rich on the main. After a good hard pull if too rich, then your plug is close to fouling and probably not sparking worth a crap. Then when off the gas, the plug just gives up the ghost due to the lower rpm and lower spark energy. Try running 32:1, might tell you something....or just slap in a smaller main and see what happens. Of course it goes without saying....one change at a time or you'll be turning in circles.

 

[suprize]

check float level, slightly high will dump fuel into the engine when you start down a hill and stall it. check by stopping on a slope and see if its dumping out the overflows

 

[suprize]

Also, remember unleaded fuels don't give reliable plug readings. you should use avgas to read a plug.

 

[everfree]

Although all the jets work in concert with each other across the full spectrum, the main jet will have very little to do with your down-low pilot mixture, just as the pilot jet will have very little to do with full-tilt-boogie main jet operation. And since that's where you seem to have the issue (hell, it could be something entirely different going on, but one must start somewhere) I think I would mess with the pilot jet first, then proceed to tune the jet needle/needle jet/main jet - in that sequence.

You may be right, though, if running too rich on the main. After a good hard pull if too rich, then your plug is close to fouling and probably not sparking worth a crap. Then when off the gas, the plug just gives up the ghost due to the lower rpm and lower spark energy. Try running 32:1, might tell you something....or just slap in a smaller main and see what happens. Of course it goes without saying....one change at a time or you'll be turning in circles.

Trying a smaller main would be quick test. You're right, one change at a time.

 

[Ron]

Although all the jets work in concert with each other across the full spectrum, the main jet will have very little to do with your down-low pilot mixture, just as the pilot jet will have very little to do with full-tilt-boogie main jet operation. And since that's where you seem to have the issue (hell, it could be something entirely different going on, but one must start somewhere) I think I would mess with the pilot jet first, then proceed to tune the jet needle/needle jet/main jet - in that sequence.


I agree with you that the main jet will have no effect at idle or low speeds.
The pilot jet however, feeds in front of the slide at all times and therefore it could have a dangerous effect if your main jet was borderline lean and you installed a smaller pilot jet. It's always best to get the pilot jet sorted out first.
You'll know the pilot jet is correct when the air screw causes the engine to quit at about a 1/2 turn out or starts to stumble at 2-1/2 turns out. The ideal adjustment range would be between 1 to 2 turns out.
If the motor continues to run fairly smooth at a 1/2 turn out the pilot is to small. If the motor keeps building revs past 2-1/2 turns out, the pilot is to big. Make sure to reduce the idle speed as you open the air screw and rev's increase.
The next step I would do would be to remove the main jet entirely, drop the needle all the way down and make sure the bike blubbers at 3/4 to full throttle. Once you've done that, put the needle clip back in the middle position and then you can safely seek out the main jet.
If the needle jet and needle profile aren't allowing sufficient fuel flow, it won't matter how big the main jet is, because it's already being restricted in the needle jet/needle combo.
Trust me, this was an expensive lesson to learn. Half a dozen bigger main jets and then a fresh bore and a new piston, before I realized I had a restriction problem in the needle jet/needle combo.
The slide cutaway and the needle jet/needle combo control the transition from closed (idle) to approx. 3/4 throttle and should be addressed individually by plug readings at a constant 1/4, 1/2 and 3/4 throttle position. Sometimes a needle that gives a good plug reading at 1/4 throttle can go rich or lean at 1/2 or 3/4 throttle and a needle with a different profile in these area is needed.
It is also critical that the floats are set properly and the petcock is flowing adequate fuel to the carb.

 

[Old Geezer]

Good advice, Ron....you've been there before. Tuning carbs is almost an art and there certainly is a learning curve - sometimes an expensive one for sure.
Good point on the pilot being active and adding some to the main circuit. I'm with you; tune the pilot first.

 

[Nordic]

Way cool John, thanks for sharing your impressions. There's just something addictive about the big bores. Probably more poop than most people need, but loads of fun. Something about more is better.

Anyone else out there (we've had 100 views so far) want to share their impressions?

Thoughts on your xc? I have a chance to grab on of the 1983 500s.
Thanks

 

[suprize]

Grab it, 500's are bit hard to get!!

 

[Old Geezer]

Thoughts on your xc? I have a chance to grab on of the 1983 500s.
Thanks

I know of one person that will roast me (Firecrackerkid :-), but...well...it's still not running yet. Just too darn busy lately to do a simple wet-side crank seal replacement (hoping that does the trick). But when it did run - and it's been several years - it was a monster. A female dog to start, but a monster nonetheless.

 

[Ron]

Good advice, Ron....you've been there before. Tuning carbs is almost an art and there certainly is a learning curve - sometimes an expensive one for sure.
Good point on the pilot being active and adding some to the main circuit. I'm with you; tune the pilot first.

I glad you didn't take offense with what I wrote. I thought it afterwards and wondered if I didn't sound like a Mr.know it all (I didn't mean to).
In trying to figure out what I want to say and how to say it, I sometimes don't stop to think about how it comes across.
The other problem with jetting is having a good assortment of main jets, pilot jets, needle jets, needles and slides for a multitude of carb sizes.

 

[firecrackerkid]

I know of one person that will roast me (Firecrackerkid :-), but...well...it's still not running yet. Just too darn busy lately to do a simple wet-side crank seal replacement (hoping that does the trick). But when it did run - and it's been several years - it was a monster. A female dog to start, but a monster nonetheless.

1 roast per customer. I've only been riding twice this year myself. I do however have a nice tan from boating

 

[Old Geezer]

1 roast per customer. I've only been riding twice this year myself. I do however have a nice tan from boating

Hey big guy, I'm cool with all the roasting anyone can dish out. The only thing constructive I've done is get my bro's CR up and running for him. Brotherly love, plus (I must admit) ME wanting to ride a Husky since mine is still fubar. I've ridden 4 times this year....so sad. But we're hitting it this weekend....Husky and Yamahas, whichever will start the easiest. Provided the countryside isn't on fire with these forecasted thunder storms brewing.

 

[ruwfo]

I'd add write your jetting numbers (carb settings) down somewhere, i've used them as a guide for other bikes. For example when my newest
250 seemed too rich on the top with the stock 430 main, i looked at my list of what was in my big bores & took it from there & got it damn
near spot on the 1st try

 

[firecrackerkid]

Hey big guy, I'm cool with all the roasting anyone can dish out. The only thing constructive I've done is get my bro's CR up and running for him. Brotherly love, plus (I must admit) ME wanting to ride a Husky since mine is still fubar. I've ridden 4 times this year....so sad. But we're hitting it this weekend....Husky and Yamahas, whichever will start the easiest. Provided the countryside isn't on fire with these forecasted thunder storms brewing.

It's gonna be hot. I have room in the truck for you and your brother if you want a ride to Washougal to watch the nationals. Leaving Friday around noon. I am trying to get a camping spot at Cascade Locks KOA.


Reservation confirmed. room in the campsite for two more.

 

[Old Geezer]

It's gonna be hot. I have room in the truck for you and your brother if you want a ride to Washougal to watch the nationals. Leaving Friday around noon. I am trying to get a camping spot at Cascade Locks KOA.
View attachment 28827

Reservation confirmed. room in the campsite for two more.

Thanks for the invite, Geary, but we've already got plans for this weekend. I wasn't aware that the Washougal National even existed. Bet it draws quite a crowd. You gonna ride in it, or just spectate?

 

[firecrackerkid]

Thanks for the invite, Geary, but we've already got plans for this weekend. I wasn't aware that the Washougal National even existed. Bet it draws quite a crowd. You gonna ride in it, or just spectate?

Lol, they would use me for traction.