Slower when hot

luke duke

New Member
Aug 6, 2008
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I decided im about run in (have about 300km on the clock) I went on a 60 km ride today and found that i lost top end after about 10 km. It is there temporarily but it doesnt hold it in fact some times misses a beat. I figure that i may be running a little rich and the plug may be oiling up at full throttle. Plug looks o.k slightly dark. I currently have a .75mm jet in on a 70cc with baffle shortened on exhaust and a few extra holes in air filter. Should i look at leaning up maybe throwing in a 70mm jet?
 

luke duke

New Member
Aug 6, 2008
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It has no problems at full throttle when climbing (lower revs) only on the flat when i get around 53km/hr. When cold it will run upto 58km/hr without missing a beat.
 

Jemma Hawtrey

New Member
Dec 29, 2007
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Essex, UK
It sounds a little odd that you are having power problems but you have a dark plug.. have you checked the choke is coming off completely?

It might also be worth looking at the ignition system - it might be as that gets hot its less efficient - also are there any parts of the wiring running close to the hot exhaust.. that might be causing the problem or be a part of it..

Jemma xx
 

MrLarkins

HS Math Teacher
Jun 17, 2008
487
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45
Arkansas
this is exactly as mine is doing...from a cold start, it runs fast (up to 32mph)...then within 5 minutes i can't get past 20 mph...and i got a black spark plug and oil around my exhaust port
 

luke duke

New Member
Aug 6, 2008
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O.K i rechecked the plug and it was a nice tan colour no carbon deposits, I might make it a little richer as a precaution. Now to get my facts straight on using the needle adjustment (the moving up and down can be confusing when you dont know which end is which) To get richer I move towards the tappered needle point to get leaner I move up on the end with the the groves (washer end no needle point!) Is this correct. Also tighten the head slightly.
 

misteright1_99

New Member
Mar 21, 2008
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Treasure Coast, Florida

MrLarkins

HS Math Teacher
Jun 17, 2008
487
0
0
45
Arkansas
well, i've already replaced ALL gaskets once AND torqued the head bolts and 2 of those snapped off...and yet, I was following NORMAN's suggestion in the other thred...my luck with this engine sucks! but I'm sticking with it and trying everything i can think of...my next try is to rejet
 

Saddletramp1200

Custom MB Buiilder
May 7, 2008
1,445
51
48
Houston, Texas
Ahhhh, your going to make me work for it. Tho rare there is a thing called (over stroking). That is when the heat in a 2 stroke reaches the point that the fuel will evaporate or de-stablize to the point of loosing it's combustion properties before reaching the combustion chamber. The molecules get stupid and refuse to detonate. That rrr sound that a stroker makes when you hold the throttle just right is over stroking. Almost power and not. Heat, pressure, and a lot of stuff have a lot to do with it. The smoother the trip to the piston the better it is. Get some metal polish and a tiny buffing wheel and shine the inside of the manifold from the carb to the motor. Make it as smooth as you can. If that don't work we will do something else :) Later Tramp (c)
 

luke duke

New Member
Aug 6, 2008
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Saddletramp you may have my diagnosed my prob!!! (not sure about answered yet!) I am running a short manifold to fit everthing in. The short manifolld means the carb is closer to the motor an does tend to heat up and i do getthe rrr sound and sometime an intermintant burst of power with it. Ill see if my richer mix will improve it when it is fine. My plug is a clean tan, Mr Larkins has a black sooty so we may have different problems.
My set up 70cc chinese, shortened muffler baffle, holes in airfilter, .75 jet. B6hsir plug(iridium version of (b6) new ignition cable, 300km on the clock. Cold top speed 58km/h, Hot top speed 50km/hr. High quality race 2-stroke used.
Will the octane of the fuel make any differance? Im using 98 octane should i try 91 the other common fuel here in New Zealand?
 

Saddletramp1200

Custom MB Buiilder
May 7, 2008
1,445
51
48
Houston, Texas
Iridium, hmmmm. It takes a LOT of volts to fire those properly. Try regapping your old plug .002 - .003 more than it is now. Tan is greaat! but may not be giving you that blue fire you need. I was using Ir plugs in my night bird but it was on NOS. It liked it better. Accel volt packs putting out around 30,000 V @ 11,500 rpm.