97 FE501 Dellorto carb tuning for altitude help

If the bike is an fe and still has the original tank on it, that black pull-knob appears to be in the fuel pump cross-over line or in the vacuum supply line that drives the pump. My '98 fc does not have anything like it, just a tap on the bottom of the tank on both sides. The fuel pump is driven by a vacuum from a barb on the on the left side of the carb flange on the head. That knob/valve may have been put in as an isolation device, may have to be pulled out to allow the vacuum to drive the pump........
At sea level here in Maine this is my jet set-up, starts 1-2 kicks regularly, hot or cold, often does NOT need the choke if outside temp is over 50 degrees -
Main jet : 172
Needle jet : 270DR
Needle : K51, 2nd or 3rd pos. up
Start jet : 45
Pilot jet : 32
Float needle jet : 300
If you need parts for your Dellorto, try here - http://www.herdan.com in Port Clinton, PA.
Tellephone is1-610-562-3155. They are far cheaper than any other carb parts suppliers, have an excellent parts supply and a gal that really knows the Dellorto stuff.

Maybe it's a hot start knob?

it is a hot start knob. it bleeds the fuel pump line to atmosphere when pulled.

Thanx, ned....
I seem to have the only 'Berg in Maine and I haven't seen another 'berg since the local so-called dealer went belly-up around 2003. My '98 parts manual doesn't seem to show anything other than the fuel pump, lines and tank on that parts page, and nothing showing on the Handlebar page so wasn't too sure.

Trying going to clip position number #3 first and see what that does. But, by raising the needle, you will loose the popping on decel and the flat spot you mention.

You may need to re adjust the fuel screw a little. Remember, set the idle speed, then adjust the fuel screw for the highest rpm, and then back in 1/8th to 1/4 turn.

Try that and let us know what you come up with. You should probably replace the DR 270 atomizer as it is probably worn too. If it's worn it will make the bike run kind of erratic and adjusting fuel screw accurately will be impossible.

Given the wide range of elevations you ride you will have to come up with a compromise.

Glad to see that you are making improvements!

Drop a pilot jet size so that you can get back in range on the fuel screw.

You really need to replace the DR 270 so that you know that it is in good condition.

The conditions you describe are, to me, typical of the tuning the Dellorto. I am curious about the decel popping going away with out any changes. However, you needed to move the needle to get rid of the flat spot, anyway.

So now that you have done that, and the fuel screw needs to be full in, that is telling you that you are too rich on the pilot circuit so drop a pilot jet size and see what happens. And that is more than likely caused by the fact that you have raised the needle and are now getting into the taper of the needle which has richened your idle mix. After reviewing the charts in the links I provided to you, I am losing my mind trying to figure out their scheme of needle adjustments. The FCR carb needle are much more logical in their needle progression.

FC 501 east jetting suggestions seem to work good for him, have you thought of trying those? Ask him what altitude he rides at.

The overheating issue you speak of. Is your radiator boiling over??? If so, you may want to put on a new radiator cap to make sure that is not the problem, they do go bad. You need to provide some more details about over heating when riding on trails, how fast are you going, what gear are you in etc.... What kind of coolant are you running ? Do not use any kind of poly propylene anti freeze/water EG engine ice. Poly propylene does not exchange heat as well as ethylene glycol and water. I just use prestone pre mixed 50/50 anti freeze. But, again, either have the cap checked by a radiator shop or replace it. This is a secondary issue at the moment, even though it might be related, you need to get your bike running right first okay?

Remember, the mixture gets richer as the bike gets hotter, your comments have proved that out.

Replace the 270 so you have eliminated that as a spoiler, I don't mean to admonish you, but, you should have done that when you replaced the needle as they do wear. You know how you said the popping on decel sort of fixed itself? In my previous post I mentioned that when they wear you will get erratic results, this is one of those signs.

After replacing the DR 270 with a new one, leave the needle at position #3. Start the bike and warm it all the way up, and try adjusting the fuel screw again. If it still wont run at idle, drop a pilot jet size and see if that gets you back in range. You did try raising the idle speed right to keep it running and that didn't help?

Dale

I came across this awhile ago and keep it on file. I just happened to breeze through it last night as I am thinking of grinding my 4.0 slide to 4.5mm.
It has some good explanations on the dellorto carb.
I dont remember who set it up or where I got it but thanks!
I was very surprised when I replaced my DR 272, big difference!

That's a nice tuning guide!!! Makes it pretty simple.

Only problem is their needle code is still kind of screwy when you are used to the FCR needle code.

Thanks for the post!

i can't find the chart right now but get a bit of grided paper from your sons maths exercize book and draw the K35 needle next to the K51. I THINK the K35 is a smidge thinner in the midrift but I can't find my paperwork this morning!

I would also consider going to a /50 slide cutaway and buy a 35 and 38PJ at the same time. get the tickover and pick up right with the PS, idle screw and PJ. get them right and then you can afford to lower the needle.

regards

Taffy

that's odd. the smallest PJ is a 33 but what do I know?

can't really say fella, your use of semantics leaves me none the wiser and quite frankly nonplussed by it all. maybe bletchley park could break down your codes but i can't!

regards

Taffy

Taffy said:

can't really say fella, your use of semantics leaves me none the wiser and quite frankly nonplussed by it all. maybe bletchley park could break down your codes but i can't!

Click to expand...

So what you're saying is it's all a bit of an Enigma?