SOHC.co.uk Forums > CB500/550
idle jet differences , 069's
fogrider:
Opening the air screws makes it worse. It starts to spit back in the air box even worse.. I started to suspect the cam timing in case someone had replaced the chain and it was slightly out. It's absolutely bang on.
It still all points to weakness and after marking the throttle grip, the bad spot is well before 1/4 open. It's a real flier once it's above 3000 rpm ( for 50bhp anyway ) and past 1/3 rd throttle, nothing wrong with the engine. No backfiring on the over-run.
Having another scan of previous similar posts, someone in New York (I think) -Nordstudio- had exactly the same problem in 2009. The thread stops before any cure is stated. Typical.
My son thinks it's the Jama silencer, can't see that, it goes too well. Unless others have had issues with a Jama ?
Sick of it for now, it's going under a sheet in the corner and the T150 is coming out for some fun.
K2-K6:
I view it that there's no particular ideal for airscrew setting, wind it down to only 1/2 turn out and it well tell you something at least.
If it covers it off then that's really telling you that it could benefit from one step up in idle jet size with the screws in more conventional range.
fogrider:
Thanks K2-K6, I have tried all ways with the idle screws. When screwing in, at less than 3/4 turn out it starts to kill the engine and I have to turn back out to at least 1. It won't wear 1/2 a turn at all. It ticks over quite well at 1 and a 1/2 turns out, at 1 and a 1/4, when fully warm, it's almost sorted, just some hesitation bottom end which is a pratt in traffic.
That reminds me of a classic Citroen dealer in Germany I buy parts off. In their very elaborate parts manual, ( English translation ), there is a description of "the enjoyment the boss gets out of screwing." I rang him and asked what it meant. When he said working with the tools and the fasteners, I explained what screwing meant in the UK.
It went quiet for a bit, then laughter.
I'll sort it, eventually, it goes too well to be anything expensive.
K2-K6:
If you want to try something that runs against conventional thinking, you can use resistor spark plugs and plug caps together and gap the plugs at the absolute minimum of specification in the manual.
I'm intrigued as to this and if it makes a difference both positive or negative on other's engines. My experience is that it's effective with leaner mixtures and helps to avoid it going toward a flat spot without forcing mixture rich to achieve it.
fogrider:
I get the idea, but when I bought the T150 it was a git to kick off. I found it had resistor plugs and 10k ohm plug caps.
I got 5k ohm caps and non resistor plugs and it became easy to start. ( it had copper leads already ).
I've tried the plug gaps at 30 thou and down to 24 thou. Could'nt tell any difference although the sparks do look poor, pinky/purple not blue, but it pulls hard, even in top, so my thought a weak spark was letting it down did'nt pan out.
I've spotted an issue with the timing marks I'm going to investigate. It's possible timing errors may be upsetting carb synch and settings.
It came with a simple foam liner instead of a paper element filter, I see some people run pods without a problem but it might be a small part of a joint enterprise in upsetting the running.
Work in progress.
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