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Discussion Starter · #1 ·
So like the title says, I am unable to get any power above a 1/3-1/2(?) throttle position, 82 CB450T...I have to short shift and get all the way up to top gear in order to maybe get 42 mph. If I attempt to give more throttle, it just gives a almost bog and slight slowdown. Does this sound more like a carb issue or a valve issue? I believe I had this same issue right before the adjusting nut came off the left intake valve and then seemed to caused the valve to rip out the valve retainer. I bought and installed new valve retainer and reinstalled it all together. I cleaned up the carbon off the valves and head while I was in there. I ended up getting new carb boots and installed the boots to the carb from the airbox properly, since whoever was in it last apparently didn't. I did the valve adjustments according the manual. although it seems to be running smoother, I attribute namely to the carb boots, it still seems to be louder than I would think it should be, but I also haven't done the balancer adjustment. even though I feel/hear like its coming from the top end still? anyone got a video of one that's not got problems and what it suppose to sound or how loud its suppose to sound like?
 

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Sounds like carbs for sure.
 

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Is it possibly fuel starvation? I don't know your particular bike, but try running it with the fuel cap open. If it works then your cap vent is clogged. As far as loud, I dunno. could be a hole? Could be the headers weren't installed properly OR if someone pulled/replaced them they didn't install the gaskets?

Otherwise - yeah . . . carbs.
 

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Discussion Starter · #4 ·
I also feel like its carbs...like maybe the main jet got plugged? I was running seafoam here and there so I wonder if something from either the fuel tank or carbs came loose and plugged the jets? I'm thinking I should probably get an inline fuel filter as a precaution.

as far as the noise it seems more like a valve train noise than exhaust leak...is it possible that having the valves on the snug side make them louder, or is it when they are looser? I know I need to do the balancer adjustment still, but I'm not hearing like its coming from the bottom end of the motor at all? I'm thinking I'm going to pickup the ultrasonic cleaner from harbor Freight. I hate cleaning Carbs lol
 

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Pop the left engine cover off and check timing and timing advance before anything else. Next check compression.
 

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I believe I had this same issue right before the adjusting nut came off the left intake valve and then seemed to caused the valve to rip out the valve retainer.

oh dear !

Anyways sounds as if you have "repaired" that situation and now have good compression on both cylinders ?

So, if all correct, bike feels like it has a fuel starvation problem ( which it may have ) or ht coil breaking down ( which it may have ) but experience tells me to check ignition advance and for ignition ht loss, which is what LDR is basically saying.

Does it feel that the engine is "surging" at about 6 k with revs dropping to about 5k then revs rise to 6 k again and repeat ???? but may calm down slightly when throttle is feathered, ie closed slightly, but still refuses to rev cleanly ????

Or, does it feel as if the engine will not rev and pull well and the exhaust header pipes are seen to glow red ?

A scope would be a brilliant bit of kit, not so much of an expensive shelf in automotive terms these days, or, alternatively, you have access to a relatively inexpensive timing light ( to show ign advance and ht "flow" ), red neon plug caps ( a good inexpensive aid to ht fault finding, a visual indication as to ht strength and ht "flow" or "disappearance" even when riding bike particularly at night ) , a mutl meter and the data needed, ie resistance values as well as ACV output data.

A modern laptop working from 12v with appropriate software and hook ups would be nice, so data can be logged when road testing you bike, but expensive relatively. Even a rolling road etc. would be nice.

All basic and slightly more advanced home informed mechanic diagnostic info is on here in various threads, even ACV data.

When you have recovered from your dizziness and have no more hair left to pull out, perform the ign checks, or, either rule them in, or rule them out, right at the beginning. Believe me it is so much easier to do the latter.

1. Start your ign system checks by disconnecting the cdi black/white wire and road test. Any difference ? Yes ? then ign kill circuit problem, chck wiring diagram. If no, then ign kill circuit probably all ok

2. Red neon plug cap/timing light checks etc., etc., etc..
 

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Discussion Starter · #7 ·

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Discussion Starter · #8 ·
those are the spoils of the repair of the valves.
 

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Discussion Starter · #9 ·
I unfortunately have no way of checking the timing or the compression atm. i dont have any surging when riding, i just get the once i get to the throttle position, i just hit a wall. i decided to take the carbs out and see whats up.
 

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Discussion Starter · #10 ·
i should prob put this to the fuel side, which i may still but i figured id start here first. the top jet is a "70", the jet under the plastic/rubber plug is a "38" (which i dont see y its under a plug for starters as i never seen that on a MX bike, anddddd i cant get the saftey wire through it at all, on either of the carbs...i can through the lil holes but not through the length of it, im pretty sure i should be able to right?), and the bottom one is a 108. i also saw the one one carb allowed the needle to fall all the way down...is that correct? is it being held up correct on the right? i dont believe its supposed to fall all the way down like that correct? image7.jpg image10.jpg image8.jpg image9.jpg
 

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Discussion Starter · #11 ·
image12.jpg image13.jpg

Meet "Frank" btw...right before i was having these issues
 

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For the carbs I'll refer you over to the Fuel section where you'll find the sticky for rebuilding VB22 carbs.
 

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Discussion Starter · #13 ·
So in case anyone views this thread in the future I’d like to finish it off and say I found my left carb fuel needle broke off and that was the culprit. Mine had the 61c but since I needed the bike to work for the next day so I could get to work since my wife needs the truck for the kids I went to the junk yard and found a few needles that were close and found some in a box... so I’m currently using a 55DC fuel needle in the left carb. And honestly, I feel like it runs better lol
 

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