450 bogging and dying when given gas - Honda Rebel Forum
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post #1 of 50 Old 02-18-2019, 12:39 AM Thread Starter
 
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450 bogging and dying when given gas

Howdy fellas, ive got an 87 450 which i bought at auction as a project which had been sitting for 3-5 yrs. The bike had not been prepped for storage so we ultrasonic cleaned what looked like black tar from the carbs, and replaced the petcock as it was leaking and was damaged. now, it would appear the bike is fueling correctly, it starts first if not second try; but whenever its given gas it just bogs out and dies. when the throttle is applied in a controlled manor, its able to idle up a little before dying. the previous owner chopped the mufflers and removed the baffles, so the air/fuel ratio is incorrect, but we've adjusted the carbs from the adjustment screw on the bottom with, as well as the idle screw but still cannot seem to get her running right. ive read about another adjustment screws covered by whats usually a brass welch plug, but i didn't want to start drilling out plugs before getting someone elses take on it. any help appreciated.
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post #2 of 50 Old 02-18-2019, 06:09 AM
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The screws at bottom of carbs are only idle mixture . Sounds like you are not getting a squirt of fuel from the acc pump jets . Plus no baffles in mufflers will cause motor to run very lean and can make it run poorly and can damage engine



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post #3 of 50 Old 02-18-2019, 07:50 AM
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AFAIK, the welch plugs were only installed on later model 250s. Don't think there are any on the 450.

Was the tank rusty, and if yes, was it cleaned? Did you install an inline fuel filter?

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

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post #4 of 50 Old 02-18-2019, 10:45 AM Thread Starter
 
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Quote:
Originally Posted by wjmrty View Post
The screws at bottom of carbs are only idle mixture . Sounds like you are not getting a squirt of fuel from the acc pump jets . Plus no baffles in mufflers will cause motor to run very lean and can make it run poorly and can damage engine
how would one go about testing the function of the accelerator pump? or moreso, what should i clean to theoretically fix this? i cleaned the carbs by placing them in the ultrasonic cleaner with a citrus based solution so i wouldnt have to remove all therubber gaskets and completely disassemble. (we took off the vacuum chamber cover and the bowl and took out jets and floats out and rebuilt with jacks rebel carb kit) so the theory is plausible, but i did have the entire accelerator pump apart and cleaned separate so im a little stumped where to go from here.
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post #5 of 50 Old 02-18-2019, 10:49 AM Thread Starter
 
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Originally Posted by flitecontrol View Post
AFAIK, the welch plugs were only installed on later model 250s. Don't think there are any on the 450.

Was the tank rusty, and if yes, was it cleaned? Did you install an inline fuel filter?
upon what visual inspection i could get of the inside of the tank, it appeared pretty clean. I know what im looking for i restored an 80's kawi km100 whole tank looked like sand was coated the inside, this was not the case. I rinsed it with gas a few times, and it still sounds like theres something in the bottom (sounds like sand in a can with water in it). and no inline fuel filter, just cleaned the one in the petcock. hope this helps
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post #6 of 50 Old 02-18-2019, 07:47 PM
 
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Remind me if that dual carb has two accelerator pumps...one for each carb?
if it does,
manually operating the accelerator pump(s?) involves filling the float bowls and turning the main throttle mechanism. if you get a squirt of fuel from that raised jet on the air filter side of the butterfly valve then it works. if not, then keep turning the throttle and maybe it will build up some pressure. you don't really need to fill the float bowl, just cover the orifice that pumps up to the accelerator pump with fuel and it should be enough..
if no fuel squirts out after replicating a throttle action then maybe the raised jet is clogged or maybe the diaphragm is too inflexible to create suction.

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post #7 of 50 Old 02-18-2019, 08:57 PM
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See post #3 here for how to test the accelerator pump. https://www.hondarebelforum.com/f76/...ed-118490.html

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 #8 of 50 Old 02-20-2019, 03:03 PM
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It sounds like carbs or spark mismanagement.

Post engine modding (cutting/chopping exhaust) does not require much in the way of tuning/adjustment save the idle screw, if any. Pre-engine changes (pod filters) do require re-jetting. I do not run pods and have not needed to re-jet. It helps to avoid the additional tuning work. Also, I like the look of the 450 air box vs. the 'bobber' pods.

All 450 rebels are 30+ years old, so I always recommend a new CDI box. I have replaced all of mine and experienced instant improvement each time. Get a multimeter and you can test yours for continuity. Both of the ones I replaced needed it. It will make your bike much more reliable.

New CDI box is the best investment I have ever made in my 450's. JRW sells them brand new!

Tune up the bike (using a service manual is best!) and check your valves too. I run 20-50 semi synthetic in my 450's per the original Jack (Baumann-there were two Jacks at JRW at one time!) of JRW that was (is?) the true Rebel Guru. He told me that ~10 years ago when I got my first 450. Love that guy, he really knew the Rebel.

I had a 'cutting-off-at-red-light' problem with my chopper and found out that it was a symptom of a bad stator. Apparently when they are going bad and get warm, they do not conduct. Would start after a few minutes (found out it was cooling) and I was on my way. Hated the lack of reliability and could not figure it out for a while. Replaced the stator and did a continuity test that proved it had gone bad. Tested the 'new' one to be sure it was OK before installing.That was right before the Lake Hope meet last year.

You should put in one of the little fuel line filters too, self explanatory. I like the 90 deg one b/c its kinda tight under the tank there.

Good luck!

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post #9 of 50 Old 02-22-2019, 07:34 AM
 
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Thanks for the mention Flight! I was thinking that
If you can creep very very slowly up on the throttle without it bogging then it's probably the accelerator pump
If not then it could be the vacuum piston not lifting due to age cracking or shrinkage and not holding a seal...
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"The bravest thing for me to do is admit when I am wrong" - unknown
HRF Answer #1 You should take the MSF Rider Course
HRF Answer #2 You need to clean your carburetor
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post #10 of 50 Old 02-26-2019, 02:29 PM Thread Starter
 
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Quote:
Originally Posted by kryton View Post
Thanks for the mention Flight! I was thinking that
If you can creep very very slowly up on the throttle without it bogging then it's probably the accelerator pump
If not then it could be the vacuum piston not lifting due to age cracking or shrinkage and not holding a seal...
Quote:
Originally Posted by flitecontrol View Post
See post #3 here for how to test the accelerator pump. https://www.hondarebelforum.com/f76/...ed-118490.html
sorry for the delayed response, ive been working a lot and have been pretty busy. so i cleaned the acc pump assembly (ultrasonic cleaned, then sprayed carb cleaner down holes and sprayed compressed air through). I can say the shot of gas is stronger but was still existent before. It is still bogging and dying. if anyone knows how to share video i took some to show symptoms. ill give a little more detail on things ive observed if this helps... the choke has to be on completely for the bike to start on a cold start. once on and warm, you can ease back about half way on the throttle before she dies. also you can only ease on the throttle when the choke is about 3/4 to half way, when its on all the way it and you try it instantly dies. also, when i place my hand covering the air intake on the left carb, theres a hard suction, then she dies. the right is slightly less suction but it revs up high if i hold my hand there and starts backfiring. right carb is also occasionally spitting gas from air intake. lastly, vacuum pistons dont appear to be moving on their own, and fiddling with them doesnt appear to do anything but make it backfire. hope this is relevant and helps, and thank you all for the help
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