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Carburetor settings on 2007 25hp Honda four-stroke

I don't have the service manual for that engine but a basic initial mixture adjustment of 1 3/4 to 2 1/2 turns out from lightly seated should get the engine starting and idling.

Then, it needs to reach operating temperature and the idle speed set before synchronizing the carbs.

If it still hesitates on acceleration after synchronizing, it's likely that there is a problem with either the dashpot diaphragm or the accel/decel check valve. If those are OK then carefully inspect the accel/decel hoses for defects or leaking.

Good luck.
 
jgmo said:
I don't have the service manual for that engine but a basic initial mixture adjustment of 1 3/4 to 2 1/2 turns out from lightly seated should get the engine starting and idling.

Then, it needs to reach operating temperature and the idle speed set before synchronizing the carbs.

If it still hesitates on acceleration after synchronizing, it's likely that there is a problem with either the dashpot diaphragm or the accel/decel check valve. If those are OK then carefully inspect the accel/decel hoses for defects or leaking.

Good luck.
Click to expand...
Thanks I'll do that.
 
Hard starting when? All the time even after warm up? Or, only when cold?

An engine that is hard starting after being warmed up and then shut down briefly might have tight valves. Check lash adjustment.

If it's only difficult to start when cold, it's likely a problem with the bystarter system.

One thing people often miss when cleaning the #1 (top) carburetor is the bystarter feeder channel in the bottom of the float bowl.

That little "tunnel" gets plugged with "mud" and often needs a small, stiff wire run through it to clear it out properly.

If that channel isn't completely clear, the bystarter supply well won't receive adequate fuel for cold start enrichment and cold starting will be difficult.

Good luck
 
Only when it's cold starts instantly when warm. You're right I had everything apart to replace a cracked jet in the bottom carburetor and didn't clean out the top bowl.
 
I don't know how hard it would be to just take the bowl off without removing the carb but, hopefully, it's "doable".

If you do have to take the carb off then also make sure the bystart pick up tube and circuit is clean by spraying carb spray liberally up in it.

Good luck.
 
Yeah, that's what I thought. Haven't actually done it before. I just worked on the carbs.

Just make sure the bystart circuit and the feed tunnel are clean and she should start easily afterwards.

The only other things that might cause hard starting on an otherwise good running engine might be low compression from excess wear or poor flow due to misadjusted valves.

There is also the possibility that the bystarter solenoid is "hanging up" and not retracting to allow fuel/air to flow. That's a rare occurance but a possibility. The bystart solenoids are typically very reliable.

You can check that when the carb is off by removing the solenoid from the carb and applying 12 volts to the solenoid connector.

Positive to brown/white wire and negative to black/ green wire.

Watch for the pin to extend, as the heater gets hot, 1/8" to 3/16" in 2 to 4 minutes.

It should then retract the same distance as the solenoid cools down after you disconnect power.

Use CAUTION when doing that because the solenoid can get quite hot and could burn you.

Good luck.
 
Thanks I did do a compression test on it top cylinder was 125 both bottom were 145 when starting cold should I turn the key on and give the bystarter a chance to warm up? I took it off and the carburetor cleaner has that red extension tube it fits down the hole that the bystarter goes in I removed the screw in the bottom of the bowl and sprayed the cleaner in the top and it was coming out the drain hole.
 
Compression sounds like it's ok but uneven so...just :"ok". Meaning it's not great but likely not causing the starting issue.

Although, you may want to do a leak down check on that top cylinder to see where the pressure loss is. It could still be a misadjusted valve causing that so, again, checking valve clearances is probably a great idea. Your choice.

As far as the bystarter, you need to understand how it works.

When the engine is cold and not running, the bystarter pin is FULLY RETRACTED and in the FULL ENRICHMENT position.
It's very similar to a fully closed butterfly type choke.

When the engine is started, voltage is supplied to the bystarter and heats it so that a wax pellet is melted and pushes the pin down to close off the extra fuel.

So, it's OPPOSITE of what you were saying. It's DEFAULTED to supply extra fuel and heats up to stop the extra fuel.

In other words, the engine should start easily when cold even if the bystarter electrical connector is unplugged.

But, if the connector is left unplugged and no voltage heats the element, then the engine will start sputtering and die from a rich mixture after a few (3 to 5) minutes.

Hopefully that's understandable.

Good luck.
 
Thanks I'm going to read that a few times too make sure it's locked in my brain lol. So is it possible it's not retracting? What would cause that? Bad bystarter or no voltage getting too it? Thanks again. Engine is running perfectly after very hard starting. And starting instantly when warn.
 
I realize...and can appreciate....that you're trying to avoid removing the carbs again.
BUT, unless you remove the bystarter first and find that it is stuck in the extended position, you really have no other option in solving the problem. The bysyarter pin not retracting is RARE. I explained how to check it in post #10 of this thread.

My guess is that the problem is more than likely the little feed channel in the BOTTOM OF THE FLOAT CHAMBER is plugged and not allowing the bystarter well to fill with fuel. Already discussed in post #5 and #7 of this thread.

You've already said that you didn't clean that so GO BACK and make sure it's TOTALLY CLEAR. It is a BASIC part of PROPERLY cleaning the #1 carburetor on this engine.

I fully explained how the bystarter works in post #12 of this thread. Go back and re-read that.
In doing that. I hope that you can understand that the bystarter needs NO POWER going to it in order to supply enrichment fuel to the carburetors for cold start.

Good luck.
 
If you are at all interested in fully understanding how these carburetors work you can order the HONDA MARINE CARBURETION MANUAL here:

Honda Marine | Shop Manuals Publications | Honda Power Products Support Publications

publications.powerequipment.honda.com publications.powerequipment.honda.com

Reference "SUPPORT MATERIALS" at the bottom of the index.

A bit tough to read because it covers many things but with lots of pictures and explanations that are very helpful.

I've read it cover to cover many times and still usually pick up something new each time. GREAT LITTLE BOOK!
 
jgmo said:
I realize...and can appreciate....that you're trying to avoid removing the carbs again.
BUT, unless you remove the bystarter first and find that it is stuck in the extended position, you really have no other option in solving the problem. The bysyarter pin not retracting is RARE. I explained how to check it in post #10 of this thread.

My guess is that the problem is more than likely the little feed channel in the BOTTOM OF THE FLOAT CHAMBER is plugged and not allowing the bystarter well to fill with fuel. Already discussed in post #5 and #7 of this thread.

You've already said that you didn't clean that so GO BACK and make sure it's TOTALLY CLEAR. It is a BASIC part of PROPERLY cleaning the #1 carburetor on this engine.

I fully explained how the bystarter works in post #12 of this thread. Go back and re-read that.
In doing that. I hope that you can understand that the bystarter needs NO POWER going to it in order to supply enrichment fuel to the carburetors for cold start.

Good luck.
Click to expand...
I removed it and it's extended I can push it back up but it just fully extends right away. Your exactly right about removing the carburetors again lol. With that bystarter being extended I'm going to replace that.
 
You CANNOT assess it by pushing it up with your finger. You need to TEST it with battery voltage as I outlined above.
If you prefer to just buy a new one....well....it's your money but you may find it's exactly the same.
 
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