Hard Starting

March 21, 2007 Update: A weak starter can cause hard starting in a perfectly tuned bike if does not spin fast enough. Details here

Is your GL1000 hard to start after sitting idle for only a week or so? This is a very common complaint … even for specimens that are perfect in every mechanical, ignition and carburetion respect. My own bike does this too. Here’s why.

The consensus of opinion on this (a common problem that plagues all bike of this vintage) is that the low “head pressure” of fuel combined with the vacuum effect of a barely vented tank and the “stickiness” of the float valves contributes to the problem. Often, the vibration of a running engine is required to get the float valves to move enough to flow fuel. If fuel has evaporated from a short lay-up, this will require quite a bit of grinding on the starter.

Modern unleaded gasoline is not your father’s petrol! Unleaded fuel is a real “witches brew” which contains many volatile, lighter components. These evaporate readily. This is why you need to keep the cap tight on your supply of gasoline for the lawn mower! Rapid evaporation can cause fresh fuel to develop a type of “staleness” which makes starting difficult in just a few days. I’m no chemist, but I’m told that smooth running in carbureted engines is way down the priority list for oil conglomerates since most autos are fuel injected these days.

(Please note that I’m not talking about long-term fuel staleness which leads to residue and gum formation after several months. Using products like “Sta-bil” can abate long term “bad fuel”.)

The GL1000 has four carburetors which feed individual cylinders of 250 cc displacement. The fuel bowls are on the smallish size even for a 250 cc cylinder. The fuel bowls are necessarily vented to the atmosphere. The surface area-to-volume ratio for these small, shallow fuel bowls is high. Combine these factors with the characteristics of modern fuel, and you have rapid evaporation of fuel components in the bowls. Hard starting is the result for two reasons:

  1. A lower fuel level effectively leans out the mixture…just when you need a richer mixture for cold starting.
  2. The fuel loses some of its “essence” when the lighter components are lost through evaporation.

Compounding all this is the fact that the GL1000 relies on a mechanical fuel pump which operates only when the engine is spinning. On most bikes, you can simply turn the petcock to “on” and gravity will cause fuel to flow and refill the bowls after a short lay-up. Not so, for the GL1000. Fuel will not flow without the aid of the fuel pump unless the tank is ¾ full or higher.

At cranking speeds, the fuel pressure is trivial (2.4 psi), so it takes quite a bit of “grinding” to refill the bowls via the fuel pump. Further, the way the four carbs are plumbed together through the plenum complicates matters when re-filling of the carb bowls in this manner. The bowls will fill sequentially starting with the two rear cylinders, then in turn the front two. What generally happens is the rear cylinders will fire before the front, so you will invariably have an extended period where the bike is only running on one, then two, then three before all cylinders are firing. Owners usually panic during this process and fear catastrophe. It’s really only a matter of (partial) fuel starvation.

Incidentally, extended cranking is a good way to fry your starter. Always crank in bursts – no longer than about 10 seconds at a time. Allow a break between tries for the starter to cool.

Here are my recommendations:

  1. Ride your GL1000 every day year round!
  2. Always use Sta-Bil fuel stabilizer to prevent long term staleness.  I recommend the Marine Formula of Sta-Bil.
  3. Use Marvel Mystery Oil (MMO) in your fuel to keep internal carb parts clean and lightly lubricated (esp. CV slides). Mix according to the recipe on the label for fuel use. This also protects your fuel tank from rusting! (MMO is not necessary if you use Marine Formula Sta-Bil …that product already contains added lubrication.)
  4. Keep your tank full at all times.
  5. Pros and cons on this one, but here’s my advice: don’t drain the fuel bowls during a typical winter lay-up of 3-6 months. I believe you are better protected from problems by having the carb bowls full of stabilized fuel for short lay-ups like this. Longer lay-ups are a different matter however.
  6. If you know that you won’t be riding in the next 6 months…DRAIN YOUR FUEL BOWLS. This is easy (consult your manual) and saves the heartache and expense of needless carb overhauls. Do this outdoors to avoid fire hazard!
  7. To refill dry bowls: First, move the bike outdoors to avoid fire hazard! Detach the fuel line to the carbs at the outlet port on the fuel pump. Attach a small funnel and carefully add about 180 cc of fresh fuel. Re-attach the fuel line to the fuel pump and you’re done.
  8. Use regular unleaded gasoline. Premium fuel is unnecessary and wasted expense. You should be fine with regular unleaded in a GL1000 unless your timing is off or you have excessive carbon buildup.
  9. Live with the fact that starting will be less than ideal after short lay-ups.

Comments

  1. Hello,
    I was just reading your comment that it’s unnecessary to use premium fuel in a GL1000, that regular fuel is recommended. That’s true, in that the factory manual states that.
    Up here in Canada, it seems that I can only obtain ethanol free fuel by using high test premium. An unfortunate trade-off possibly. What’s your opinion regarding this?

    Thank you……….Dave

  2. I made a movie yesterday. Please admire the ‘excellent’ starting of a GL1000 after standing still for a while 🙁

  3. https://www.youtube.com/watch?v=O402Xsi_sSM&feature=youtu.be

    I made a movie yesterday, Have a look at it and admire the ‘excellent’ starting of a GL1000 starts after standing still for a while …….

  4. Just out of curiosity, couldn’t you just turn off the fuel petcock while the engine is running to drain the fuel bowls? You probably wouldn’t get all the fuel out, but it would be better than not draining the bowls at all, I would think. I’ve done this the last two years on my ’77 XS750 and my wife’s ’77 CB750A with no ill effect; just wondering if the new-to-me ’78 GL1000 is sufficiently different to make this a bad idea…

    • Not recommended for many reasons. One is the “incomplete drain” issue you mention.

      Others:

      1. Small jet orifice sizes
      2. Complex and lengthy plenum fuel circuits
      3. The mechanical fuel pump is “stressed” by running the engine with the petcock “off”

Trackbacks

  1. […] Use STABIL brand fuel stabilizer in your fuel. Most GL1000s owners are busy, travel a lot and live in a climate with a real winter. They don’t ride their bikes nearly as often as they should. For these reasons, I recommend that you run STABIL year round. This will help you avoid problems with varnish gumming up your carbs from lack of use. See my Tech Tip on“Hard Starting” […]

  2. […]  Vintage Hondas like early GoldWings and CBXs have fairly robust starters. They do have wear issues that can lead to sluggish starting…especially when the engine is very hot. More on that issue later. A weak starter can cause hard starting…even if the bike is perfectly tuned. More on hard starting here. […]

  3. […] Use STABIL brand fuel stabilizer in your fuel. Most GL1000s owners are busy, travel a lot and live in a climate with a real winter. They don’t ride their bikes nearly as often as they should. For these reasons, I recommend that you run STABIL year round. This will help you avoid problems with varnish gumming up your carbs from lack of use. See my Tech Tip on“Hard Starting” […]

  4. […] Use STABIL brand fuel stabilizer in your fuel. Most GL1000s owners are busy, travel a lot and live in a climate with a real winter. They don’t ride their bikes nearly as often as they should. For these reasons, I recommend that you run the STABIL product year round. This will help you avoid problems with varnish gumming up your carbs from lack of use. See my Tech Tip on Hard Starting. […]

Speak Your Mind

*