This probably will be the last update until I get my 21mm PHBG racing clone from China in a month or so.
The
needle set came in today and I figured out that my w20 needle is actually is some weird size. It's the same tip end as a w7 (approx 1.4mm) but with over 20mm of taper.
Tried out the w11, w5, w7 needles on various clip settings and the best setup so far seems to be the w5 on the 2nd from the richest notch. This was going purely off of head temp (after redline for 1/4+ mile), exhaust smoke volume, max achievable rpm (and accompanying noise), and 'seat of the pants feel'.
With it being 106f right now I have to run fairly rich to keep the motor from getting too terribly hot. The highest I read was about 460f on the leanest notch on the w11 needle (1.8mm tip, 2.5mm shaft 86-8700 rpm) and my last run on the current w5 2nd from richest notch (1.4mm tip, 2.46mm shaft 83-8400rpm) was about 4-420f.
The biggest difference I've noticed has been my low end is actually usable now. Before if you were trying to accelerate from 2k rpm, it was not happening because of how stupidly early it was getting on the needle. Now with an 18mm taper, it actually accelerates, albeit not very fast, but it can pull from that low without roasting the clutch. Also, it strangely idles better now, despite the slightly smaller diameter (2.46 vs 2.50mm) which probably has something to due with how long the taper was on the old needle. *MID POST EDIT* Just double checked the measurements on that needle and the taper is easily 24-26mm if not longer. That would explain the low-end power issues.
I might get around to dropping my jet size to the next one down but it's forecasted to be over 100f until August 29th where it should finally drop down to only 98f for a couple of days before going back up to over 100f. Working on anything out in the garage in that heat just plain sucks.
I will, however, swap out my 44t back to the 36t so I can get some better mileage and better top speed within the next day or two. Was only running a 44 because cruising at 20mph (when I ride with my pedal powered neighbor on 15+ mile rides) the super early needle was beyond painful.
The motor would get super loaded up on excess fuel-oil and just guzzled gas. Literally every 1/4 mile or so I'd have to clutch in and redline it over and over to clear out the crazy build up. Where running the 44t brought the rpms up just over 1k at 20mph and it wouldn't load up quite as bad. Now it'll happily cruise at 2k rpm without 4 stroking the entire f***ing time, let alone at ~4k rpm where the 36 likes to be at 20mph. I'm willing to bet I increased my mileage 25% or better with just a different needle. *MID POST EDIT* Maybe not on the mileage changing, I've seemingly used damn near half a tank in the last couple days and I've only ridden 10ish miles (3.5l tank).
That and when it comes in, I'll be installing that new carburetor because of
TWO MORE MM OF OPENING BABY!!!
That and hopefully with the correct, non jerry-rigged atomizer/bushing combo, it'll run a touch better and be easier to tune.
I do have two questions/concerns:
1: Is it normal to only really need to use the first maybe 1/8th of the throttle? Like I can get to within a few miles an hour of topping out with seemingly very little throttle. Literally, 1/8-3/16 throttle is more than enough to get 80-90% of the way to redline, the only difference the rest of the throttle makes is how quickly I get there. Once it's there, I can maintain it with as little as 3/16 throttle and once at or basically on redline the last 20% of throttle keeps it there.
EDIT: Found a couple of very very informative threads about some of the various mechanics with these carbs and I forgot about the progression system. Because of my rather rich idle jet, the progression system is easily allowing enough fuel to get pulled as the RPMs increase without really needing to touch the throttle as it'll meet the fuel demands of the increased airflow.
2: Considering the ambient temperature is/will be 105F or higher for the next 2-3 months, what is a safe
maximum temperature for these motors to run at? By
maximum, I mean for a period of 1-2 mins of WOT before riding normally. The highest reading I got after going 1/4 mile WOT was 460f, I'm not sure at what temperatures these motors start to seize up at.
What would be a safe
constant/running temperature?
After riding 3.5 miles home just after the sun started to set (104F), running it harder than normal, I got a reading of 365f or so. I've read that a constant 400-450f can be handled but I thought I'd ask. This is on a stock head, the temperature is being measured with an IR thermometer near or on the base of the spark plug, I've spray painted the head and plug with black paint to help with the accuracy of the reading (worst case, the gun is adjustable).
I'll be buying a CHT gauge with my next paycheck so I can keep an eye on temperatures, damn this PHX heat. Or I might spend the money instead on a 6cc fred head, better cooling = more better, right?
EDIT: Found
this thread here talking about maximum CHTs and it sounds like I'm still quite within safe temperatures. Just got worried since it was finally getting hot enough to start to burn off some of the crap that has built up on it, along with the black spray paint (not high temp stuff). This gives me more confidence in going down a couple of jet sizes, I'm fairly certain that it's still far too rich at WOT.
EDIT 2: After blasting around for about 1.5 miles at 8k rpm or higher, I only reached a peak(ish) temp of 460f in 94f weather (I'll test in a few hrs when its 106-107). Since I won't be running that high rpm for any longer than that, I think I'm good to lean it out some more if it's really needed but I shouldn't have to.