97 FE501 Dellorto carb tuning for altitude help

I have a 97' FE501 with the PHM40 ZS carb that is running way too rich for my altitude (I live in Colorado at about 8500ft. above sea level). This is the second year I've had the bike and it ran OK when I first got it I had to turn the mixture screw all the way in, and back off the idle screw to a high idle speed to keep it from dieing at idle. Also the iridium plug was very black and I noticed the clear licence plate cover gets black from the exhaust. I let it sit over the winter and it started OK with full choke, but tended to die at high idle and starting after was hard. Ive always used 91 octane with stp octane booster at about 1oz. per gallon. This year It got to the point were It would die when I came to idle or first rolled off the throttle and random hesitation, plus it has always been very difficult to restart once it dies, so I cleaned the carb changed the oil, plug, gas, etc., and just run 91 octane without the stp. It seems to be running better now but i haven't put many hours on it yet, mixture screw still all the way in, but I've been able to lower the idle speed. I think the bike is pretty much stock, I have 2 uni air filters fitted to the frame and if there was ever a baffle on the stock exhaust I can't see it or it must be pretty far back there. Currently the jets in the carb are 195 main? witch is stuck in the part it screws into, DR270, 45 choke?, 42 the small one under the 195 I'm guessing this is the pilot? 300 were the fuel comes in, K51 needle on the 3rd clip from top. I also need a new oil drain plug and oil screen with o rings. I ride anywhere from 5500 ft. above sea level and rarely up to 12000ft., so I guess 8500 feet jetting would be a good compromise. Looking for some advise and a place to buy parts at a descent $ USD. Thanks in advance, I tried to provide as much info as possible hope it makes sense.

Jason

from the owner's do c at the left on the home page:
http://www.husaberg.org/wiki/index.php? ... arburation

dellortos are toward the bottom.
(your pilot is way too fat. most would be running a 35 or less at that altitude)

Yes, I read the doc, I just didn't see much on altitude adjustment other than trial and error, I was just hoping for a good starting point. Thanks for the advice on the pilot jet. I just took her out for a 3 hour ride after cleaning the carb, and now the throttle or something in the carb is sticking causing it to rev too high at low rpm's (kind of like cruise control, not a good thing on trails). If I pull in the clutch and rev the throttle it goes back to normal. Is something sticking in the carb or do I need to adjust the throttle cable? Also more info on jet/needle adjustment would be appreciated.

If you go to the Doc section that Ned talks about, all the way at the bottom there is a setting that has some mod's to the carb.

However with your stock carb, and what you have posted here is what I suggest.

First, as Ned says drop to at least a 35 pilot, maybe even just go straight to a 33, get it running and see if you can get in range, between 1 and 3 turns out on the fuel screw at idle. Ideally, between 1 & 1/4 turns out to 2 & 1/2 turns out. If you get it set more towards 2 & 1/2 turns out at your base riding elevation, this will give you good tuneability as the temperature increases, or as you head up to higher elevations. My friend log jump used to keep a small screw driver in a piece of pvc tubing on his bars so he could tune his bike during the day, just a 1/4 turn can make all the difference. Even more so, if you are starting out at 8500 and going up to 12,000.

Set the the idle speed to around 1500, and adjust the fuel screw to highest idle speed, then 1/4 turn clockwise=leaner. If necessary during fuel screw setting turn the idle speed down lower so that your fuel screw adjustments are more noticeable. If you set the idle speed too high, it will make it difficult to tune, as your changes to the fuel screw will be less noticeable. Too high an idle speed will also make your bike hard to start, as the reduced intake impulse from the larger throttle opening will not pull in enough fuel.

Second, drop the needle at least one clip to position #2. If it bogs on quick throttle opening UNDER LOAD NOT ON THE STAND. Then that's too much.

Third, start working your way down on the main jet, I might drop to a 188 to start with. Keep in mind that changes you make to the main jet will have an overall effect on the jetting, a rough rule of thumb is on needle clip position is = to about 10 in main jet size, EG a drop from position #3 to #2 "could" equal a main jet size drop from a 195 to a 185. You'll just have to experiment to come up with the best results.

Make the changes ONE AT A TIME AND KEEP NOTES!!!! I can't stress this enough about making one change at a time or you'll either be incredibly lucky, or hopelessly lost.

You've made a good move by going to straight 91 octane fuel at that elevation and dropping the octane booster. You might even try 89 octane mixed with 91, or even go straight to 89. If it pings or detonates then go back up to 91. But as you have already experienced, just the change you've made by getting rid of the octane booster has shown results. With as high as you are, the cylinder pressure under compression is so much lower than at lower elevations, you don't need all the anti knock that higher octane fuel provides.

As far as your throttle sticking goes, do you have enough play in the throttle cable? I would imagine you do, or blipping the throttle wouldn't help.

Seeing how you just cleaned the carb, which means you had everything apart, perhaps the cable got re routed or kinked?

Also, if the needle and needle jet are original, they might need replacing anyway as they tend to wear over time, thus allowing more fuel to get past, and this will have you chasing your tail as far as jetting goes.

So, start off with number #1 first. If memory serves I used to run a 33 or 35 in my 94 501 at 4000' elevation. Get it starting good first, then go after the rest. And remember, when you change the main jet, it's going to have an overall effect on the jetting, especially needle position.

Dellorto are notorious for being finicky, so what you are looking for here is a good compromise, you can use the fuel screw to make the best of an overall good setting throughout the day.

Thanks, I'll order those parts and start one step at a time.

Jason

Got the parts ordered, thanks all for the help. Few more ?'s though. My headlight dims at idle. The bike starts easily from cold, but it dies sometimes at idle when warm (due to improper jetting I presume) I can kick start for ever with no luck, I have to pull start it frequently. Taffy mentioned something about the stator. Could this be causing the hard starting or is it probably just the jetting? Also what is the knob on the carb that pulls toward the back of the bike for? If it is the stator what are the best options and $.

Thanks, Jason

I ordered a DR272 atomizer, but my carb has the DR270. What's the difference? Also what about the choke jet I think mine is a 45 is it worth messing with?

Thanks

The black cable operated knob? The choke?
If you are running rich you probably want the 270.
Best option for the stator is a sparks rewind.
http://www.uk-motoplat.com/

Is my throttle supposed to automatically close when released like most bikes? Sorry for all the posts I just keep thinking of stuff. If so I may have another slight problem.

berger said:

The black cable operated knob? The choke?
If you are running rich you probably want the 270.
Best option for the stator is a sparks rewind.
http://www.uk-motoplat.com/

Click to expand...

Yes, the one in front and lower than choke that pulls back. what does it do?

jwk1977 said:

Got the parts ordered, thanks all for the help. Few more ?'s though. My headlight dims at idle. The bike starts easily from cold, but it dies sometimes at idle when warm (due to improper jetting I presume) I can kick start for ever with no luck, I have to pull start it frequently. Taffy mentioned something about the stator. Could this be causing the hard starting or is it probably just the jetting? Also what is the knob on the carb that pulls toward the back of the bike for? If it is the stator what are the best options and $.

Thanks, Jason

Click to expand...

Please post a picture of your carb, so we can see the choke, I think that's the knob you are talking about.

The reason it doesn't start when warm is because it doesn't run when it's warm.

jwk1977 said:

Is my throttle supposed to automatically close when released like most bikes? Sorry for all the posts I just keep thinking of stuff. If so I may have another slight problem.

Click to expand...

Yes! The throttle should snap closed when released. If it is not, pull the throttle tube off the bike and clean everything. Inspect the throttle cable on both ends to make sure you do not have any broken wires. Buy a cable luber and with the throttle cable removed, flush out the cable with some thing like Tri flow, or other thin lubricant that will not dry out or gum up.

I agree with Berger about the needle jet size. I "think" the needle jet size is in hundredths of a millimeter in diameter. So the 272 is going to have a bigger inside diameter than than a 270, thus allowing more fuel to get by.

I was looking at the work shop manual for the 98 model, the Enduro bikes are jetted pretty fat when compared to the FC or moto cross models.

Enduro 195 main, DR 272 needle, K51 needle #2, and a 45 pilot

FC 172 main, DR 270 needle, K51 needle #2, and a 45 pilot.

These settings are for sea level, and both are with the PHM 40 carb.

Also stated in the manual, fuel screw range 1 &1/2 to 2 &1/2. So get a pilot in there so that the bike stays running within the fuel screw range. You will get no where except tired until then. If you keep pull starting your bike, sooner or later you're going to eat it.

After further review, you have the flip up type choke lever, that's the older style phm.

Further, I suggest you read through this guide http://www.ducatimeccanica.com/dellorto ... lorto.html it will give you a better understandingah of whatah your are dealing withah.

Here's another table I found just doing a simple google search.
http://www.thisoldtractor.com/gtbender/ ... mizers.htm

Just figured something else out, and need you to confirm this, is your mixture screw on the air filter side or the motor side of the carb? If it's on the air filter side and you've got it screwed in all the way, then you are shutting off the air to the pilot circuit. I had assumed up to this point that it was on the engine side, and that would adjust the fuel, not the air. So let's get that straightened out first. Either way, the mixture screw should be set around 1.5 turns out to begin with.

DaleEO said:

jwk1977 said:

Is my throttle supposed to automatically close when released like most bikes? Sorry for all the posts I just keep thinking of stuff. If so I may have another slight problem.

Click to expand...

Yes! The throttle should snap closed when released. If it is not, pull the throttle tube off the bike and clean everything. Inspect the throttle cable on both ends to make sure you do not have any broken wires. Buy a cable luber and with the throttle cable removed, flush out the cable with some thing like Tri flow, or other thin lubricant that will not dry out or gum up.

I agree with Berger about the needle jet size. I "think" the needle jet size is in hundredths of a millimeter in diameter. So the 272 is going to have a bigger inside diameter than than a 270, thus allowing more fuel to get by.

I was looking at the work shop manual for the 98 model, the Enduro bikes are jetted pretty fat when compared to the FC or moto cross models.

Enduro 195 main, DR 272 needle, K51 needle #2, and a 45 pilot

FC 172 main, DR 270 needle, K51 needle #2, and a 45 pilot.

These settings are for sea level, and both are with the PHM 40 carb.

Also stated in the manual, fuel screw range 1 &1/2 to 2 &1/2. So get a pilot in there so that the bike stays running within the fuel screw range. You will get no where except tired until then. If you keep pull starting your bike, sooner or later you're going to eat it.

After further review, you have the flip up type choke lever, that's the older style phm.

Further, I suggest you read through this guide http://www.ducatimeccanica.com/dellorto ... lorto.html it will give you a better understandingah of whatah your are dealing withah.

Here's another table I found just doing a simple google search.
http://www.thisoldtractor.com/gtbender/ ... mizers.htm

Just figured something else out, and need you to confirm this, is your mixture screw on the air filter side or the motor side of the carb? If it's on the air filter side and you've got it screwed in all the way, then you are shutting off the air to the pilot circuit. I had assumed up to this point that it was on the engine side, and that would adjust the fuel, not the air. So let's get that straightened out first. Either way, the mixture screw should be set around 1.5 turns out to begin with.

Click to expand...

Yes, the mixture screw is on the motor side. This picture should make things easier. I'll take apart my throttle assembly and clean that up. What would cause it to not run when warm?

Thanks, Jason

jwk1977 said:

berger said:

The black cable operated knob? The choke?
If you are running rich you probably want the 270.
Best option for the stator is a sparks rewind.
http://www.uk-motoplat.com/

Click to expand...

Yes, the one in front and lower than choke that pulls back. what does it do?

Click to expand...

Now that I look at it, the flat knob that says pull on it I was talking about isn't even on the carb, just close. Still wonder what it's for though, looks like some thing to do with fuel. Sorry, I'm definitely not a mechanic.

[/quote]

What would cause it to not run when warm?

Thanks, Jason[/quote]

Having the mixture or fuel screw turned all the way in.

jwk1977 said:

jwk1977 said:

berger said:

The black cable operated knob? The choke?
If you are running rich you probably want the 270.
Best option for the stator is a sparks rewind.
http://www.uk-motoplat.com/

Click to expand...

Yes, the one in front and lower than choke that pulls back. what does it do?

Click to expand...

Now that I look at it, the flat knob that says pull on it I was talking about isn't even on the carb, just close. Still wonder what it's for though, looks like some thing to do with fuel. Sorry, I'm definitely not a mechanic.

Click to expand...

The choke is added enrichment for cold starting. You pull it out during cold start for anywhere from 15 seconds to a minute for cold start. If you pull it out while while the engine is warm it will run very rich.
This is all basic mechanical knoweldge. You never had to start a gas powered lawn tool?

I know what a choke is, I was just under the impression it was the top lever, not the flat knob that isn't on the carb, what is that knob? (see attached picture)

What would cause it to not run when warm?

Thanks, Jason[/quote]

Having the mixture or fuel screw turned all the way in.[/quote]

So essentially my rich jetting would be the cause?

yes

jwk1977 said:

I know what a choke is, I was just under the impression it was the top lever, not the flat knob that isn't on the carb, what is that knob? (see attached picture)

Click to expand...

I dont have alot of experience with pre 2000 bikes, but i can honestly say I have never seen a knob like that. I got no clue.