Background: I got this bike for free from my father and at the time it wasn't running, however besides some fluid changes and whatnot, the only other thing it needed was carb work. The last time he had tried to work on it, gas was pouring out of one of the air vent tubes and it caught on fire. Once I started working on it, I pulled the carbs off, pulled them apart off the rack, replaced all the o-rings, the fuel Ts, and the air vent Ts (along with the main one) however when I was putting it back together, I was looking through the service manual and noticed that it said they were for emissions stuff so I made the mistake of plugging them. Along with replacing that stuff, I also went through and thoroughly cleaned the carbs (checked the diaphragms, they were in good shape) and used a rebuild kit off eBay to go through and replace the main and slow get, the float valve, and the pilot screw (though again, I made the mistake of not seeing how far they were backed out so I had to mess with that for a while). After putting it all back together, it ran like crap so I went back through the service manual to see what I missed, and low and behold, it was the pilot screws.

I eventually set them at .75 out from the bottom and it ran better but still not quite right. It'd struggle in any gear it was in and it'd only really be able to hit about 7/8k rpm in 1st before it just lost power. I took them to a shop to have them properly balanced thinking that was the issue but that didn't solve it either so when I got it back, I remember those air vent fittings and unclogged them. This caused it to run significantly better but it's still not quite there. Now, it'll be a little slow in first gear from about 2k-4k and then it'll pick up with pretty much no issues till redline but as soon as I shift down into 2nd and try and give it WOT, it'll bog down right around 8k rpm. Along with this, if I'm just cruising in 2nd gear with it at around 4k rpm, it's very jerky and doesn't really run well. On top of this The majority of the time I'm going from 45/50mph in 2nd gear (8k rmp ish) to a stop or even just slowing down, when I pull the clutch in and hold it in for a second, the engine will die. One more thing to note is when in neutral, I can rev it up to redline and it does just fine (albeit a slow throttle initial throttle response from 2-4k rpm) but once in gear (especially 2nd and 3rd) is when it starts to lack power

Some of the things I've tried since unclogging the air vent Ts (mind you, the hoses for them arent connected so they just breathe into open air)

• adjust the pilot screws starting at .7, then 2, and then 2.5 turns out. It performed pretty much the same at .7 and 2 turns out but at 2.5 it started running rougher so I backed it off and I'm going to try it at 1.5
• I originally was running a fuel filter but since I was having issues with that, I took it out. It's now a direct line from tank to pump to carbs
• I've tested the flow rate of the pump and I was getting roughly 1100-1200 cc/min
• I've made sure that it's not the pump pulling a vacuum on the tank by cracking open the fuel cap and doing a pull in 2nd and had the same issue
• When I was going through and cleaning the carbs, I had swapped out the main and slow gets with the ones from the eBay rebuild kit but I swapped those back out for the ones that were in it (making sure they're in the right carbs) and it ran better after that but didn't fix it (did this at about the same time I unclogged the air vent Ts)
• I've tried running it without the air filter in, it performs slightly worse than with it in (making sure it's pointed in the right direction)
• I've also checked valve clearance already, they're within spec

I've largely run out of ideas as to what to test for at this point. I found this thread about it being the fuel pump connectors when under load and I've probably going to try it however at idle (after having the bowls empty) I can hear it working to fill them up fairly quickly. Any help/suggestions/advice on this would be much appreciated but it's kicking my but right now and I can't figure out why.

 

I would send the carbs off for a rebuild - you’ve messed with far to much to easily diagnose what you’ve buggered up.

 

Not exactly looking to pay someone else at this point since the cost to balance them alone was around 200$ or so, but on top of that they are pretty much back to how they were before I started messing with them except for a couple small things (2 of the float valves and the 4 pilot screws)

 

Shoppes do not have expertise with carbs! They don't have some 70-yr old wizard in back that's been dealing with carbs for decades and had experience with thousands of rebuilds.

For that cost, you could've had them professionally restored, with float-level adjusted and sync/balanced. Proper carb restoration requires A LOT more work:

- scrubbing out all secret hidden passages in carb-body with brushes and PEA-based fuel-system cleaner
- poking out all bleed holes with soft copper wire of matching gauge
- ultrasonic soak everything
- micro soda-blast
- replace all rubbers, float-valves, fuel-rail O-rings, pilot-screw O-rings, float-bowl seals
- set and test float-levels
- sync carbs with manometers

All for less than $200 from the pros. Carbs will come back brand-new and bike will run like fresh off showroom floor. I send mine in every winter while race-bike undergoes rebuild. I race in stock class, so factory-fresh clean carbs are one of few mods I can have that gives me advantage over others who are using clogged dirty carbs causing temperamental bikes.

https://customcarbservices.com

 

I'll look into it as a last resort kind of thing but ideally, I want to be able to figure it out without spending too much more money on it at this point. If it comes down to it, I'll send it off but that'd require a lot of cost ontop of what they'd charge. Thanks for the information though!

 

do stuff you haven't done yet from list above. Any steps skipped will result in carbs being less than factory-fresh clean and bike still won't run right.

Expert mechanics who can rebuild engines with their teeth and hands tied behind back have had to pull carbs 4-5x for ever deeper cleaning until they were factory-fresh clean. I suggest any time you pull carbs, do complete restoration job so you won't have to pull them again. If it can be further disassembled and cleaned, do it.

Scrub-brushes from amazon:
Ultrasonic cleaner:
Micro soda-blaster: https://vaporhoningtechnologies.com/...-a-carburetor/

Manometers:

Buy about 10x sets of used carbs from eBay to practice. Will end up destroying many in process of learning to restore carbs back to factory-fresh condition. It's not easy process.

Also only buy OEM carb parts from authorised Honda dealer. Most of "kits" out there have incompatible parts, many of those jets aren't even matched within same kit. Taper of float-valves don't match seat, wrong O-ring sizes, etc.

 

Bit of an update, decided to just order a set of carbs on eBay that's supposedly good to go so hopefully that solves the issues.

 

Sorry to jump in here a little late. Not knocking your purchasing decision but even if the new carbs are in perfect condition, you will still need to sync them. They can be bench synced but hats just to get them in a rough ballpark starting point. A proper sync can only be accomplished on the bike on which they will live.

 

Unless they are brand-new in shrink-wrap from authorised Honda dealer, they are most likely used and just as dirty and clogged as yours.