Total noob, 2008 Rebel 250, acceleration issues, misfiring? - Page 6 - Honda Rebel Forum
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post #51 of 60 Old 11-25-2019, 06:45 PM
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Originally Posted by 1Surfrider View Post
I'm keeping my speed down with this carb adjust, the A-valve disconnect experiment. Easy removal/replace. Leave the rod in the arm loop. No prob. Simple rpm and throttle adjustments removing the A-valve.
Accelerator pumps are very common on bike carbs. From the number of times you have suggested this modification, it's clear you are a believer in bypassing the accelerator pump. But I'm wondering how so many motorcycle engineers that design carbs for many brands of motorcycles, could be wrong?

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'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
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post #52 of 60 Old 11-25-2019, 11:22 PM Thread Starter
 
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Originally Posted by rebel250jane View Post
Alright everyone, the diagnosis came back... one of you mentioned a compression test and hit it right on the head. The mechanic checked the carburetor (all good), valve clearances (all good), spark/coil/airfilter (all good) it ended up being one of the cylinders. If I remember correctly, one was at 110 psi and the other at around 150 psi. Basically one was broken. He recommended not to replace just the one, but both, saying if one was this bad then the other wasn't too far behind.
Actually I picked up the bike today, my bad it was actually that one side was a little above 150 psi (normal) and the other was 10 psi lol so way worse than I wrote
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post #53 of 60 Old 11-25-2019, 11:30 PM
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Originally Posted by 1Surfrider View Post
So 2019 was the last year or will there be a 2020 year 250CMX Rebel?
2016 was the last production year for the Rebel 250. In 2017 they came out with the Rebel 300 and 500 models.

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 #54 of 60 Old 11-26-2019, 09:35 AM
 
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Quote:
Originally Posted by flitecontrol View Post
Accelerator pumps are very common on bike carbs. From the number of times you have suggested this modification, it's clear you are a believer in bypassing the accelerator pump. But I'm wondering how so many motorcycle engineers that design carbs for many brands of motorcycles, could be wrong?
I had trouble understanding what his meaning was. I hadn't heard of disconnecting the accelerator pump on the Rebel. But it doesn't sound like a great idea. The logic behind the accelerator pump is that when first opening the throttle (air control, so letting in more air), the AFR tends to go lean because there is a bit of a lag of the fuel delivery. But with the pump, the pump is connected to the throttle valve and it simultaneously pumps a bit a fuel into the increased airflow in an attempt to steady the AFR.

Is it perfect? According to the AFR gauge no. But without the AFR gauge pointing out what's actually going on, the accelerator pump does 1 very important job, very effectively. It prevents a stumble when opening the throttle. Our buttometer would never detect exactly what happens with the AFR, but it will detect a stumble. The accelerator pump does a great job of smoothing out the power delivery when opening the throttle by preventing a stumble. That said, I would not disconnect it. The Rebel engine, like my Scamp's LA360 (old school V really likes fuel. Maybe its a 2 valve engine thing dunno.


7milesout

2016 Honda Rebel 250 - The "Piglet."
AFR sensor equipped and downsized to a 0.105" main jet.
The only changes so far.
Bought on 6/29/19 with 44 miles.
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post #55 of 60 Old 11-26-2019, 03:22 PM
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Here's a diagram of the carb. The part in question is number eight, and Honda calls it a pump. If you watch when opening the throttle, you can see it only functions when the throttle is first opened. https://www.cheapcycleparts.com/oemp...31c/carburetor

It's possible that the person who opened the carb didn't put things back together properly, or possibly it needs cleaning, which is a common issue with these bikes.

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 #56 of 60 Old 11-26-2019, 05:52 PM
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The rod moves a diaphragm inside the pump assembly, squirting extra gas into the carb. Once it has done that, it doesn't add any more gas to the fuel mixture until the throttle is rolled off and then on again. It's a one time thing, unlike a valve that provides a measured, continuous, flow.

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 #57 of 60 Old 01-09-2020, 04:00 PM Thread Starter
 
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Soo... the rebel is at a different mechanic now (long story) "getting fixed". They opened it up and decided that the engine looks fine, but the reason for the compression test failure was actually a bent exhaust valve and not the cylinders. Honestly, I don't know which mechanic to believe right now I feel like I've been given the run around so many times thus far. This would the 3rd mechanic to take a look at this rebel (although the first mechanic was just for a tune up).

Not sure if anyone is still following.. Just an update because the misfiring and no-power has officially NOT been fixed and the mystery has not been solved...
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post #58 of 60 Old 01-09-2020, 05:17 PM
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Sorry you're having these problems. So you don't pay for another repair that doesn't work, ask them to do a compression test with you observing to confirm they fixed the problem before you pay them.

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 #59 of 60 Old 01-09-2020, 05:50 PM
 
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rebeljane - We're still watching and hoping this all comes out good in the end. A bent valve sounds reasonable. Not sure what would lead to that. Perhaps wrong weight oil or low oil and lots of high rpm usage (from a previous owner)?

2016 Honda Rebel 250 - The "Piglet."
AFR sensor equipped and downsized to a 0.105" main jet.
The only changes so far.
Bought on 6/29/19 with 44 miles.
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post #60 of 60 Old 01-09-2020, 10:17 PM
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There have been several reports of bent valve stems on Rebels that were stored for long periods and then started up. Lack of lubrication probably caused the problem.

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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