Slower when hot

luke duke · #1 08-22-2008, 11:45 PM

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 · #2 08-23-2008, 12:29 AM

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.

**Bikeguy Joe** · #3 08-23-2008, 06:46 AM

What color is your plug?

Jemma Hawtrey · #4 08-23-2008, 11:02 AM

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

misteright1_99 · #5 08-23-2008, 01:15 PM

Check you head bolts (when cold). Look for leaks (oil) around the base of the cylinder and head.

MrLarkins · #6 08-23-2008, 04:46 PM

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 · #7 08-23-2008, 04:48 PM

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 · #8 08-23-2008, 07:42 PM

You are correct on the needle adjustment, clip towards the tapered end id richer, towards the flat end leaner. I would not tighten the head bolts unless they need to be. If you have a torque wrench I would torque them to spec in a cross pattern. Do you see any oils stains around the base or head?

http://motorbicycling.com/f3/cylinde...pecs-2934.html

misteright1_99 · #9 08-23-2008, 07:47 PM

Quote:

Originally Posted by MrLarkins

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

Sounds like a bad head gasket or loose head bolts to me....Might want to check them with a torque wrench also, in a cross pattern.........

http://motorbicycling.com/f3/cylinde...pecs-2934.html

MrLarkins · #10 08-23-2008, 09:34 PM

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