97 FE501 Dellorto carb tuning for altitude help

Maybe it's a hot start knob?

DaleEO said:

Maybe it's a hot start knob?

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You could be right, It does seem to help a little sometimes when trying to restart my bike when hot.
Thanks for all the input everybody.

The knob has two hoses coming out of it ones goes up to a little k&N like breather filter the other tee's in to a hose that goes to the right side of my tank to what I believe is a fuel filter maybe, says Mikuni.

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.

Did all the things dale EO recommended. Thanks Dale! The 33 pilot seems good I'm now at 2 turns out on fuel screw. I replaced my K51 needle and moved to clip position 2 and put in a 188 main jet. Didn't replace the dr 270 atomizer. It doesn't overheat anymore and seems to run pretty damn good. I want the carb to be optimized for about 9000ft.
The pilot jet is good, The 188 main may be a little lean for 9000. The exhaust pops when I let off the throttle/engine brake, condition gets better when engine warms up, And there seems to be a little dead spot in the powerband somewhere between 1/2 and 3/4 throttle. I drove it down to 6000ft. today and it did OK, but It did hesitate at full throttle a few times. I'm thinking I should go up a few sizes on the main jet or move needle clip to position 3. any recommendations?

Thanks, Jason

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!

DaleEO said:

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!

Click to expand...

Just like you said it went away. But my fuel screw likes to be turned in all the way again at idle. Should I move back to position #2 and raise the main jet size, or just go to a smaller pilot jet. I plan an replacing the atomizer but it doesn't seem to be efffecting the changes I make right now.

Oh yeah, The popping on decel went away before I moved to position #3, must have just needed to be broke in or something, but the flat spot didn't until I moved the needle clip. And my overheating didn't completely go away, It would still get too warm and not want to run when I ride trails, again this was before I moved to position #3. I flushed the radiator and changed coolant, also lowered oil level slightly. I haven't done a long enough ride since the clip position change to see if that helped with the overheating.

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!

No boiling over of the radiator, and I use the pre mix 50/50 glycol water.

Yes, I raised the Idle speed and it's running OK. It never overheats when I'm going fast, just when I'm riding in tight woods rocky situations (slow), but I do tend to get on the throttle.

What size pilot jet should I drop to if the bike was idleing good with a 33pj on needle position #2 mixture screw 2 turns out? But I needed to move to needle position #3 to get rid of flat spot at 1/2 to 3/4 throttle. Now the fuel mixture screw likes to be all the way in to acheive highest idle speed.

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

So I got the new 270DR atomizer, nice increase in overall throttle response and power. Didn't really effect my jetting situation much though. I tried dropping to a 32 and a 30 PJ. The mixture screw still likes to be turned all the way in. I am still on needle K51 position 3 to eliminate the flat spot I experienced at 1/2 throttle or so. and running a 188 MJ. The bike starts first kick and runs like a bat out of hell. I drilled holes in the plastic thing in front of my radiator, not sure if I still have the overheating issue because I haven't rode long enough. But I probably still do because of the mixture screw issue. It will run at 1 or 2 turns out, but the RPM's noticeably increase when the screw is all the way in. I checked the o ring on the idle and mixture screws and they look good. I'm very happy with the way the bike runs now other than at idle. I don't really want to mess with throttle slide cutouts and all those mods. So do I go to needle position 2 and raise the PJ, or go to a different needle? Also as said before I think my stator might need to be rewound as my headlight dims at idle.

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!

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

I've seen the film and the americans broke the code while surfing behind a submarine! :twisted: :twisted:

regards

Taffy