low end gets worse and worse

i know this has been covered but i cant think of how to phrase this question in the search.



65 metra, cast matched

19 phbg, 80 main, 37 idle

proma gp exhaust

stock clutch.

plug chops look good, maybe a little rich at the very top.

low end is real nice when i first start the bike, but the longer i ride the worse it gets. its doesnt sound or feel like a jetting issue but i suppose it could be. feels more like my clutch the culprit.

im wondering if as the ATF gets nice and hot the clutch isnt grabbing like it should. someone suggested using Motul ATF, as it supposedly works much better. any suggestions?

kind of elementary, but after taking a week and a half off mopeds (mm vacation) im drawing a blank.

Re: low end gets worse and worse

how long heat fade sets in after like 10 minutes of riding IMO which takes way all the balls and just makes it smooth

Re: low end gets worse and worse

heat fade?

my ride to work is barely ten minutes long. two stop signs and then like 10 or so stop lights downtown. the low end is shot by the second stop light.

Re: low end gets worse and worse

bad rings?

Re: low end gets worse and worse

doubt it.

this kit is only a few hundred miles past break-in. never soft seized.

Re: low end gets worse and worse

move needle up maybe just a guess could be ok on startup

but to rich at low throttle when the engine warms up

like I said just a guess

Re: low end gets worse and worse

did you break it in right?, maby when the metal expands you get an air leak or something when it starts to loose power put it on the centerstand and spray carb cleaner around the manifold and see what happens, maby its your ignition as well

Re: low end gets worse and worse

yeah i might try playing with the needle a bit, its just the fact that the bike's performance changes as the engine heats up that makes me think its not really a carburation issue.

break-in was fine, no air leaks at all, timing is dead on.

Re: low end gets worse and worse

Try riding it until its all the way warmed up and the low end is at its worst. Then put it up on the stand and reset your idle mixture screw like this:

Set your idle speed to be faster than normal. Unscrew your idle mix screw a quarter turn at a time until the engine starts choking a bit. It usually takes about 3 or 4 seconds ofter each quarter turn until the engine starts reacting to the change. As soon as the engine starts choking, screw it back in a quarter turn. Now you know where your max setting is.

From there start turning in the idle mix screw a quarter or eighth of a turn at a time until the engine runs as smoothly as possible, i.e. the RPMs are very consistant and solid. Remember to wait a few seconds between each asjustment to let it take effect. Now reset your idle speed back to normal and turn off your engine. Write down how many turns out your mixture screw is from all the way in for future reference.

Now go for a spin and see how the low end feels. If the low end still doesn't seem good, try turning in the idle mixture screw another quarter turn and see if it gets better or worse. If better, try another quarter or eighth turn in and see if it gets better or worse again. If worse, back it off to where it was best before. Eventually you'll find the ideal setting.

Re: low end gets worse and worse

If what I worte above doesn't help, then try leaning your needle one notch.

In the Dellorto manual they always say to make sure your engine it at full operating temp before adjusting, so it still could be a carb tuning issue. Engine temp definitely makes a difference.

Re: low end gets worse and worse

) Cupermcnewbster ( /

what kind of plug are you running. Kinda sounds like heat fade/ carb tuning issue.

Re: low end gets worse and worse

NGK b7hs. what is heat fade?

damn it tim. i hate tuning my idle. fine.

Re: low end gets worse and worse

daddy tim knows whats up

Re: low end gets worse and worse

Low end that progressively gets worse while riding is always due to heat. but not always in the same way.

"heat fade" is the process of your combustion getting too hot after everything heats up. Basically after you ride around for a while, usually 5 min or so but every bike is different, your bike starts to lose alot of low end. this is because the spark plug is too hot. To fix this go to a higher # plug, if you run a 6 go to s 7 if a 7 go 8 etc.

The second heat related progressive loss of low end is due to the transmission fluid getting too hot and slipping like a motha. This happens when clutches are tuned out drastically, they are shot, or the type of fluid used is not correct. Fluids like mobil 1 5w20 and non moto grade tranny fluid will slip more as they heat up (some tuners tune with this in mind) More constant fluids like moto grade atf will always grab the same and break down less with heat.

Its easy to tell if the clutch slip is the culprit, if the loss in low end is resulting a prolonged clutch engagement or a clutch that "double shifts" ie catches then releases and catches again, then its obviously a slipping issue.

Other reasons bikes have bad lowend are as follows:

timing is too retarded

jetting/tuning is drastically off

air leaks, especially in the magneto side crank seal.

gearing is too tall

intake is too big

Steps I'd take to trouble shoot if its not the clutch, if you think it might be the clutch open that shit up and check it out, replace the fluid with moto grade atf (not car atf) as well.

throw in a cooler plug--- test

check for air leaks around the magneto side seal, obvious ones will have goo coming out of them. if you find one, rebuild the motor.

set timing to full advance on the stator and set the points gap to a a hairline (i really need to figure out what i set the timing too "hairline" is kinda vague, just make sure its really small and still firing)---test

pop in a a larger (or stock) pilot jet and re tune that circuit as instructed above.--test

btw 37 sounds kinda small for the pilot jet, just my opinion tho, i never tuned a 65 metra.

Re: low end gets worse and worse

oh i should mention that if you are overheating and experiencing "heat fade" and the points are full advance the gap might be too big, thus the advantage of advanced timing for lowend gets eliminated by the amount of heat too advanced timing starts to generate. this is likely the case if you find your ped only running well on b9 and b10 plugs and overheating/getting "heat fade" on anything less.

Re: low end gets worse and worse

wow elliot thanks.

i was having problems with this setup backfiring a few weeks ago so i spent some time making sure my timing is right. i believe i have it set just slightly retarded but ill check again to be sure.

thanks for the other suggestions too. now i know what to try.

Re: low end gets worse and worse

elliot said in a lot of words what I was going to say in a few.

Put a b9hs in that baby and see if it helps

Re: low end gets worse and worse

my buddy had to tighten his head bolts intake nuts and ehxaust header for the first 100 mile increments of his kit break in.

Re: low end gets worse and worse


Re: low end gets worse and worse

u should tighten that stuff again after the motor heats up but not continually, once the aluminum fuses its set, don't touch it.

also timing retarded on [uch = bad performance

stock puch ignitions like full advance and small points gaps, trust me. even at full advance they fire at like 1mm b4 TDC with a hair line point gap, open it another hairline and u will unleaseh"the power"

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