Diagnosing a carb/acceleration issue - Honda Rebel Forum
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post #1 of 8 Old 12-07-2019, 03:06 PM Thread Starter
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Diagnosing a carb/acceleration issue

Hey all, working on my 14 Rebel for the first time and hoping to get some clarity on an issue. Been reading this forum for a bit and it's been pretty helpful thus far.

Picked up the bike used with just around 3k miles 2 years ago, and from day one it had a bit of a flat spot in the acceleration where it would start and idle ok, but I'd get it out of the driveway and it would frequently sputter and stall. If I pulled over and let it sit idling for a minute or two I could usually work past the issue and the bike would run ok after that.

This past summer I had an un-anticipated break in riding and let the bike sit for way too long with almost a full tank of gas. When I got back on last month, it would stall every time I came to a stop. I drained the gas, pulled the carb and took it apart. It looks pretty clean from what I can tell, but there's one part coming off the acceleration diaphragm that has two dark-ish rings on it (pics attached). Is it possible that's what was causing the flat spot? The engine has also bogged down somewhat on a couple of steep hills but I'm not sure if that was related.

I have a spray can of Berryman's but from what I have seen people are soaking parts for 48 hours (after removing anything non-metal). I have tried cleaning this several times now but these dark rings remain. Any advice is much appreciated.
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post #2 of 8 Old 12-07-2019, 05:34 PM
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Welcome. Some of the most common engine issues are carb related. I don't think the minor rings on the accelerator pump shaft have anything to do with how it performs. If you decide to soak the carb, I would do it for up to a week as 48 hours is a minimum IMO. One member soaked/cleaned their carb five times before getting it completely clean. After soaking and rinsing the parts with water, use high pressure air to blow out every orifice. Canned air and carb spray aren't powerful enough.

If you have access to an ultrasonic cleaner, they do a great job of cleaning a carb in a relatively short time.

Keepin' all the left over parts. Gonna use 'em to build another bike!

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post #3 of 8 Old 12-07-2019, 05:57 PM Thread Starter
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Originally Posted by flitecontrol View Post
One member soaked/cleaned their carb five times before getting it completely clean.
Damn. Well that's good to know. Sounds like even with a lower miles bike it wouldn't hurt since I've already got the carb disassembled. I'll give it a shot, thanks for the input!
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post #4 of 8 Old 12-07-2019, 09:33 PM
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Mileage isn't as important as how long the bike sat with gas in the carb. Does it run better with the choke (fuel enrichment circuit) always on? If so, that's a classic sign of a dirty carb.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
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post #5 of 8 Old 12-08-2019, 05:40 PM Thread Starter
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Mileage isn't as important as how long the bike sat with gas in the carb. Does it run better with the choke (fuel enrichment circuit) always on? If so, that's a classic sign of a dirty carb.
Aside from when I would first start it up, the bike never had to run with the choke on. The issue I had noticed from day one was that flat spot with the throttle about 1/4 turn open. Once the bike had been cruising for 5 minutes or so, that seemed to work itself out, but it was definitely frustrating for a new rider. Last month was the first time I had to deal with it sitting too long with fuel in the tank (my bad, rookie move). Don't know how the previous owner treated it, aside from the fact that it was obviously dropped on it's left side. I did notice that the idle would sometimes change when the bars were turned from left to center, but I suspect when they tried fixing it up they didn't route all the cables correctly. Something else to look into.

Lucky for me I seem to have stumbled onto a pretty-easy-to-work-on machine so this is all a good education.
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post #6 of 8 Old 12-08-2019, 06:33 PM
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The idle change when the handlebars are turned does sound like a cable routing issue. If you have a Honda service manual, there are a series of diagrams showing correct cable routing. Pages 1-18 through 1-23 in my copy.

Does this sound familiar and address your throttle issue? https://www.hondarebelforum.com/f76/...tle-74170.html

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
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post #7 of 8 Old 12-08-2019, 07:34 PM Thread Starter
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Originally Posted by flitecontrol View Post
The idle change when the handlebars are turned does sound like a cable routing issue. If you have a Honda service manual, there are a series of diagrams showing correct cable routing. Pages 1-18 through 1-23 in my copy.

Does this sound familiar and address your throttle issue? https://www.hondarebelforum.com/f76/...tle-74170.html
Yep, got a service manual and plan to check that routing.

Fuel delivery issue was in roughly the same in that spot as the post you referenced. Super helpful.
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post #8 of 8 Old 12-10-2019, 12:46 PM
 
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dh78757 - I have 1% of the experience flightcontrol has. He is VERY good with this stuff. The only contribution I think I can make is suggest to read the first couple pages of the 'Rebel AFR' thread, and it will give you an idea of how your bike is supposed to run based on AFR. Read until you get to the first chart(s).

It's helpful for what to expect from a) steady state cruising, and b) wide open throttle acceleration.

If I were to take a guess or two in your case, I would say in some instances, your bike needed to be choked / enriched. There's not a thing wrong with enriching it. But just don't forget to work it back off as the engine warms up. When you say it would stall, but would seem to work it's way out. Well, I'm guessing it was too lean, and choking it would have resolved that and you could have rode without it stalling.

Seems some tend to think that choke is only for a temperate cold engine. That's not the whole truth. In the middle of summer, if your engine is down to ambient temperature from sitting all night for example, that's considered a cold engine and it doesn't hurt to pull the choke. Just don't forget about working it back to off. These engines carbs are tuned so well from the factory though that most don't "require" to be choked. But pulling the choke will improve cold engine performance. I generally only pull mine about halfway, and just push it back in little bits at a time once I feel like the engine is actually warming up.


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2016 Honda Rebel 250 - The "Piglet."
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Bought on 6/29/19 with 44 miles.
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