Choke problems ZL 900

[alex-germany]

Since 2009, i have bought my Eliminator, i have problems with the choke function, when the engine is cold.
When i use the choke full, the rpm goes up to 4000rpm. When i use the choke to lower the rpm to round about
1500 - 2500rpm, i don't can use the throttle without engine stalling. Only if i use the choke minimal, i can drive
without stall, but the rpm is bad. I feels like the mixture is very lean, if i use the choke normaly.

In the years, i have two or three times clean the carbs, but the problem remained.

On my ninjy and our zephyr we don't have the problem never.

Are the choke jets on the eliminator to lean?

Best regards, Alex

 

[rkerg]

Have you checked that the fuel bowls are filling to the correct level?

 

[87kawzl]

Have the valves been adjusted recently? That can cause some grief with starting/running properly

 

[wuputt]

Also, using Premium fuel can cause hard starting. Run 87 or 89 octane will start much quicker than 91!

 

[Niek]

Hi Wuputt, not wanting to be smart or anything, but your comment about lower octane fuels surprised me. So I had a little play with Claude and it came up with the following:

(edit: the statement about using premium fuel being wasteful in an engine designed to run on regular fuel is not correct; the cleaning properties of premium fuel are beneficial among other things)

Does using premium fuel (high octane) cause hard starting in a motorcycle? Why or why not?

No, using premium/high-octane fuel does not cause hard starting in a motorcycle. In fact, octane rating has essentially nothing to do with starting difficulty. Here's why:

**What octane actually does**

Octane rating measures a fuel's *resistance to pre-ignition* (knocking/pinging) — how well it resists igniting under pressure before the spark plug fires. Higher octane simply means the fuel is harder to ignite prematurely under compression.

**Why it doesn't cause hard starting**

Starting difficulty is governed by completely different factors:

- **Volatility (RVP)** — how readily fuel vaporizes at low temperatures. This is what matters for cold starts. Premium fuel has very similar volatility to regular fuel; the difference is negligible for starting.
- **The spark plug still ignites the mixture** — regardless of octane, the spark plug provides more than enough energy to ignite the air/fuel mixture. High octane doesn't make the fuel "harder to light" with a spark.

- **Fuel delivery** — carb jetting, injector function, choke/enrichment circuit, and fuel pressure affect starting far more than octane.

**When octane *can* matter for a motorcycle**

- If your engine is *designed* for premium (high compression, performance engine), using it is correct and beneficial.
- If your engine is designed for regular fuel, using premium is simply wasteful — it won't help or hurt, just costs more.
- Using *lower* octane than recommended in a high-compression engine can cause knock and power loss, but that's the opposite scenario.

**Actual causes of hard starting** to investigate instead: old/stale fuel, a dirty or stuck carburetor float/needle, a weak battery, fouled spark plugs, a faulty choke circuit, or incorrect valve clearances.

So if someone is experiencing hard starting after switching to premium, the octane itself isn't the culprit — something else is going on.

 

[wuputt]

I did not consult "Claude" just commenting from personal experience.

 

[Niek]

Fair enough. I've had not had any bad experiences with premium fuel. If anything, the higher ethanol content of cheap E10 petrol is notorious for causing issues, hence why many European motorcyclists opt to use premium petrol. Again, not having a go at you, just interested to see experiences can vary between bikes.