RD350LC Fuel ratio tuning

[mcferreira100]

Bike missing around 3-4000rpm and was advised its running bit lean. So was advised further to adjust throttle needle 1 notch up to 2nd from top (its on 3rd middle notch right now). Thought I could just adjust airscrew for richer mix. Would like some opinions on this.

[JimR]

is this a 1980 model ? if so there was a load of mods done to get over this problem ... from memory one of the progression holes in the carbs had to be enlarged main jet was upped 1 over standard ....you may have a bike that never had the mods done

[dt502001]

Well if its lean then going up with the clip will make it leaner if anything you want to go down. But why are you driving around at 3-4 k rpm no power there they don't turn on till 5k + and thats where they like to run keeps the plugs clean and not loading up the motor.Chuging around a 3k you will foul plugs and mabey thats what happening. Do a plug chop and check what they look like.

[mcferreira100]

Engine completely overhauled so running it in and was advised to go no higher than 7000rpm thru 1st 2nd and 3rd for 1000km. So taking it very easy right now. Not even done 100km yet on new motor.

Check my thread RD350LC Stood 20 years. Its the early 4LO serial which should make it 80-81.

If its normal to have this miss then its fine..just want to be sure. What about turning in airscrews?..at the moment they`re set 1.5 turns out.

[dt502001]

Your bike is black and red so it a 82,, 81's were wite and blue 1980 were 400's air cooled.

1.5 turns is just a base setting,, no 2 bikes run the same,, tuning a 2t is abit of a black art and every adjustment you make should be done 1 at a time so you can tell what worked and what dosen't so.

If the bike is pulling clean and strong to 7k and the plug is a nice coffey with cream colour then its all fine don't go messing with it till it's broke in.Fix you front brake first.

and run it at 5k to 7k

[mcferreira100]

You make sense DT50 as it was advertised as an 82 from the seller. Will check the plugs after some more mileage. Motor also needs to loosen up as well I guess.

Asked the guy who did my engine to take it for a spin to see how its going as he knows the RD`s, he reckoned the rev counter was running slow..not sure how much slower..maybe due to it standing so long. Is this possible?

Front brake is fixed.

[JimR]

Your bike is black and red so it a 82,, 81's were wite and blue 1980 were 400's air cooled.

1.5 turns is just a base setting,, no 2 bikes run the same,, tuning a 2t is abit of a black art and every adjustment you make should be done 1 at a time so you can tell what worked and what dosen't so.

If the bike is pulling clean and strong to 7k and the plug is a nice coffey with cream colour then its all fine don't go messing with it till it's broke in.Fix you front brake first.

and run it at 5k to 7k

hmm rd400's in 1979 where white and red with red mag wheels the modals with 4L0 prefix are watercooled (4L1 for the 250) and there is a differnce between tuning and geting the bike to run right

[dt502001]

Show me a 400 lc never seen one ever. Rd /z 350's are so easy to detrmin what year they are if they have orignal paint on them every year had spefic colours scheems save for the Kenny roberts special built in 1985 and came in standard colours also every other year had 1 paint scheem for every year.

You make sense DT50 as it was advertised as an 82 from the seller. Will check the plugs after some more mileage. Motor also needs to loosen up as well I guess.

Asked the guy who did my engine to take it for a spin to see how its going as he knows the RD`s, he reckoned the rev counter was running slow..not sure how much slower..maybe due to it standing so long. Is this possible?

Front brake is fixed.

Only if he is mentaly able to read rpms of a engine.. Old cables will lie a bit more than new,as they have been streched and wound more BUT but they all lie,It's not like you bike is going to blow up the instant you run it to red line.

[mcferreira100]

Turned airscrews in 1/2 turn and it was worse. Turned them out to 2.5 turns from all the way in and its MUCH better. So she`s wanting more air. He must have meant its running too rich..it does seem to have been guzzling fuel. So wondering should I still set throttle needles one notch up.

[dt502001]

I hope you didn't think you would get good gas milage they didn't put that big of a fuel tank on for nothing.

As I said black art and no 2 bikes run the same your going to have to do plug chops and determin what your next step should be.

Be for warned though the leaner you get it the better it will run till you go past the right amount then it will sieze up,for a road bike its best to stay on the rich side( safe side) than get it to lean.

Also you cant tune a bike unless you can run it full out so for now leave it rich and finnish breaking in the motor. Then worry about tuneing it.

[mcferreira100]

Well didn`t expect good mileage but its only doing 31mpg on last fillup.

Spec on these bikes is 43mpg (that`s probly if u cruising all day long at decent speeds). But sure it will get better once run in.

[nayruf]

Hi

I used to have my DT running pretty lean trying to get as much out of it was a little quicker it was running a little warmer and it holed a piston,

After doing some research on the net some write ups were saying that ethanol (C2H6O) in today’s fuel adds to the air in the air/fuel mix, it’s a minimal amount but it can be enough to make a lean running motor that little bit leaner, because of this I have found on my DT that if I run the bike a little on the fuel rich side the bike runs a little better, also the some of the same forums were recommending using fully synthetic two stroke oil as the water content in ethanol was breaking down the boundary layer of oil on the internals of the motor. I don’t know what the ethanol content is in the fuel you have but here I think we have a 5 or 10% mix probably soon to become a 15% mix.

I don't know what others will think but I have now done about 2000 miles on the DT and it has not played up yet,

[dt502001]

43 mpg down hill with the wind to your back,rider weight 80lbs maybe 30 is about right of all the rd/rz's I had never had one do better than 30 ish normaly less cause I beat them all the time,they are such great wheelie bikes

[mcferreira100]

I`m not worried about getting more power out of it..just this flat spot between 3500 and 4000rpm makes it awkward to ride as its running at that rev range at cruising speed. Its jerking and has no power between those revs.

Also bit worried about autolube setup as it doesn`t seem to be smoking much (not that I would know how much they should smoke). Must check manual and maybe adjust cable bit tighter. Will feel more comfortable adding a little 2stroke to tank during run in period.

[dt502001]

Mc thats the nature of the beast if you try to rollon the power in 6th at 3500 it's going to be like wet toast, soggie, you have to adjust your riding style to suite a 350 2t. If you want to get up and go kick it back 2 gears and the power will be there. Any thing much below 5 k and the bike is not even starting to work they are happiest between 5 and 9k rpm they beg to be reved.

All the tuning in the world wont fix what your complaining about thats why yamaha put the power valve on in 83. If you tune it to run at 3500 then it wont run right at 9000.

Have you done a plug chop to see where you are on the rich lean scale? All you need to do is get the mix right so you don't hole a piston or size it up then adjust your riding style.

[mcferreira100]

Havent checked plugs yet.

What I should have added its running smooth in high gear before 3500rpm (cruising on flat or downhill). Obviously not much power then..I gear down before getting to uphill sections. Then just taking it to 5-7000rpm first 3 gears on each pullaway..and gearing down now and then while cruising. Almost done 200km now.