Hey hey everybody. This is my first post on this forum, so please be gentle. I have some questions regarding carburetor jetting that I hope someone can help me out with. I have an FL350 that I have rebuilt from the ground up over the past few years and I'm down to the final tuning. Along the way I had to scrap the stock carb and get a new one. A previous owner jacked up the stock unit so badly it was effectively useless so, I picked up a Keihin PWK Airstriker 35mm based on recommendations. I installed it on the machine and she fired right up and ran ok right out of the box. It was quite rich with the jets that come stock in the PWK35 but at least I could start the process. The PWK35 comes with a #48 pilot, #160 main jet, and jet needle DEK.

My cylinder is bored 2 over and I have a DIY airbox that is roughly factory dimensions. The cylinder head is still air cooled. Currently in the carb I'm running the Honda factory spec #45 pilot jet, #155 main, and the DEK needle. I'm using a 32:1 mix. Everything from idle to about 1/4 throttle is perfect. From 1/4 to 1/2 it seems pretty good. I can hold it at 1/2 throttle and pick up plenty of speed. Anything past 1/2-5/8 throttle though, and it falls on it's face. I cannot get it to WOT (Wide Open Throttle), it just bogs and loses all power. So anyway, here are some numbers for y'all to chew on.

Top speed: 52.8 (GPS Measured)
Should it go faster?
Max RPM: 6328
Should it rev higher?
Cylinder Head Temp: 360 (F)
Is this in a safe range for this machine?
Exhaust Gas Temp: 1050 (F)
This seems about 100 degrees too low?
(RPM,CHT,EGT measured with a Digatron)

So here is the thing. I've tried the main jet on either side of the #155 and both make the machine run poorly. I can't get over 40 MPH and there is no power anywhere above 1/4 throttle with either the #152 (lean 1/8-1/2) or #158 (Rich 1/8+). Yet the #155 is still too rich above 1/2 throttle. I've tried raising the clip on the needle, this results in no power below 1/2 throttle. I have tried running with the airbox lid open and it offers no improvement on the top end, it does however, make for a lean condition at partial throttle. I have tried a needle with the same length and diameter but with less taper, CEK. This seemed like it made things worse across the board. I'm fairly stumped. I feel like I'm really close but yet way off. Is there any possibility that this issue can be remedied by adjusting the pull of the throttle cable?
Thanks in advance!

Hi and welcome! Do you know if your neutral/reverse safety switch has been bypassed? I had a machine that the sensor had went bad and limited the Odyssey. Use the “pilotodyssey.com google search” button at the top of the page to search the forum for previous post about reverse/neutral rev limiter. Hope this helps.

What fuel are you running?

Hi there New Guy

You said you rebuilt it ? did you do a Frame repaint. If so
there is a Ground wire on the frame front left of Engine on the cross
member undo the bolt and file / sand all the paint off and re attach.

That may help.

wyeeoddy

Welcome new guy.
Can't help you with jetting because I don't run that carb. Others can chime in.
Top speed of an FL350 is 64.3 mph with a 24" rear tire. Confirmed by gps and truck speedometer.
Here is a thread on that reverse limiter bypass: http://pilotodyssey.com/PO/viewtopic.php?t=1064
CAUTION: it will now start WITHOUT being in neutral. There are a few bad stories here on that. You have been warned.

Your machine is still air cooled you say -- AVGAS -- you have been warned. You said your machine is on second over bore -- hummmmm -- I wonder why. You have been warned.

Edit: Are you sure your choke is closed all the way ??
Also sounds like it's flooding so I ask: Did you mod the fuel system in anyway ?? The "T" check valve must be in the line to return fuel to the tank. Is any fuel running on the ground when you are just sitting there idleing ?? Float valve may not be closing.

Thank you for the warm welcome and the replies. I have been chasing this gremlin for a while now, and have tried almost everything that you folks have suggested with the exception of higher octane fuel. I've been stalking the forum for about three years, but I've never posted before, perhaps out of pride.

The neutral safety switch is connected as it should be and checks out electrically. I have run the machine with it connected and bypassed, and it has zero effect on the problem I'm having. I'm certain that this is not the cause.

Yes, I have repainted the frame, but I made sure to rough up to bare metal for all frame grounds. I have been working with twelve volt electronics for many years and know this drill very well. Continuity between any ground and the negative post on the battery is well under half an ohm. There is almost zero voltage drop across the negative side as well. This is not the cause either.

It is still air cooled, but I have installed a auxiliary fan to help with this. I was going to go water cooled when I did the rebuild, but I just didn't have the coin at the time. Plus I figured that she ran for 30 years as an air cooled machine, so why bother until there is a physical need to go that route. For what it's worth, it does at least have the post recall "Y" head.

I run a 32:1 mix of 93 octane (Shell, BP, or Mobil) and Honda GN2 oil. Race gas and avgas are quite rare in my area. I understand that pump gas is a bit on the lower end of the octane rating, but I do believe that the manual specs 93 as being the minimum acceptable.

No modifications to the fuel system other than a replacement fuel pump which I sourced from Oddatv. The check valve, tee, and filter are in place as well. The float level is spot on. No fuel on the ground since the new carb install. The choke could be possibly an issue, however, I can see a witness mark on the rubber plug where it makes contact with the nipple in the carb. I'll quintuple check, but this seems unlikely as well. Especially since it runs so well up to half throttle. Also, if I pull the choke at speed when the Engine is warmed up, it stalls.

The reason the for cylinder being bored over twice is as follows: I rebuilt the Engine due to a bad lower end air leak. Also partially because of my OCD. I replaced the stock piston at this time. Unfortunately, I gave it to a local college with a motorcycle program to do the boring. The students did a rather poor job of it and I had to have it bored again. I took it to a professional the second time around and all is well. Right around 138 PSI @ 70 degrees F.

I am currently running 24" Kenda Bear Claws on the rear. So it would seem that I'm down about 20% on the top speed.

I am going to stop you right there. You say you have been trolling this site for about 3 years. So then you must have read a lot of poofkaboom threads. You also seem to know what you are talking about. You have covered all the basics.
I have run two 3" bilge fans on my machines when they were still air cooled. It didn't help. An air cooled Engine requires a tremendous amount of cfm. The engines are behind the seat so that don't help the cfm required. What kills an oddy is not so much the heat but the fuel detonation. These deto strikes are deadly to an oddy. You mention the manual specs 93 octane but I think you missed something. Look closer (section 4-1) because it states 93 LEADED octane. Leaded fuel was fazed out starting in 1973 and was not completely eliminated until 1996. The lead prevents detonation of the fuel. Remember these machines were made in the stone age -- 1985. The fuel of today is not the same as the stone age fuel we used to get. Also as the Engine gets hot this does not help the detonation thing -- it makes it worse.
The fuel thing here on this site is a contentious issue. I posted a thread on who runs high octane fuel and who runs pump gas -- it was 50/50 in the votes. I am not saying you can't run it but beware, there is evidence on this site as proof.
I think I am getting way off base here right now because you are looking for a low top end issue.

By the way nice machine.

I know this sounds stupid but are you sure the carb is going to full throttle (cable adjustment) ??

Worn out belt ??

Here is a thread I found on jetting: viewtopic.php?f=1&t=4963

Something smells here and it's not me.
I have re-read this thread -- slooooowly this time.
It won't matter what fuel you are running based on the issue you are describing. Avgas won't magically make the thing run from half throttle to full throttle. This seems to be a whole other issue.
I am not questioning your mechanical skills at all but did you pressure/vacuum this Engine before you started it up ?? Did you do this test with the intake manifold on ?? I wonder if you have an air leak. This would prevent you from pulling fuel under full load.

Also do you have access to another carb ??
Problem with that airstriker possibly ??
You said previous owner F----D up the original carb. What did he do ?? Is it useable for a test ??

Based on the thread I posted about the striker jetting your 155 is good.

No one seems to have answered your question on head temperature so I will take a shot.
You say you are running 360'F and from what I have read 450'F seems to be about as much as you should run. Apparently over that and you can get detonation of the fuel.
Also how do you know you are running that temp (seems like an exact number you posted there) ??
Do you have a plug sensor unit installed ??

The more I read this opening statement the more I believe you are running out of fuel.
You appear to be able to roll into half throttle and then it starts to fall on its face. That just screams fuel flow to me.
1) Is your fuel pump putting out 4.5 oz in 10 seconds flow ??
2) Is your fuel tank clean and more importantly are your pick up lines clear ??
3) Could there be a blockage (rust) in the fuel petcock ??

DIY airbox?...We need pics as that might be your prob right there.

Canadian oddy, you are excellent. Thank you for digging in on this issue. I sincerely appreciate the effort. Bugeye59 brings up a good point as well. I will go down the list of things mentioned since my last post.
Indeed, I have read may of the horror stories regarding air cooled Engine failure. I have also read quite a few in which people have run their machines form many years without failure. Perhaps this is luck of the draw? Either way my goal when I began the rebuild was to get the machine running as it was from the factory and go from there. I was really trying to get familiar with the stock setup before introducing more variables. So on to the meat...

Now that you mention it, I had forgotten that the minimum octane ratings were based on leaded fuel. I am well aware of the benefits of the lead in relation to detonation. I just kind of pushed that fact aside because leaded fuel isn't an option. Also thinking that there have been improvements to the unleaded fuels of today to help mitigate detonation. As well as like you mentioned, many folks are running pump gas in their machines. That said, running a higher octane fuel is probably something I should consider for the long run.

The drive belt is brand new. In fact, just about everything on the machine is new. I literally have my heart and soul in to this thing. Every part was torn down, sand blasted, and painted. Every seal, bearing, and gasket in both the Engine and trans have been replaced, even packed the crankcase seals with fuel resistant grease as recommended. I swapped all of the hardware for stainless steel with the exception of the grade 5 & 8 fasteners. New u joints, new wheel bearings, the front arms were reworked by those cats out in Arizona. I ordered new Heim joints from the UK for the rear trailing arms and camber adjusters. New Works shocks at all four corners. The brake system has been completely rebuilt front and rear, along with stainless lines. I also replaced all of the crappy electrical connectors with GM weather packs. Seriously, name it and it has either been replaced, re-built, or re-worked. Mechanically the buggy is as good or better than the day Honda floated it over to the States back in '85. So I'm sure you can understand my dismay with the driveability.

Thanks for that link to the thread on jetting the PWK35. Definitely seems like I should be in the ballpark with the current jetting.

I will have to look into the throttle cable adjustment again. I suspect that this could at least be a contributing factor.

As far as pressure testing the bottom end, this is one thing I did not personally have my eyes on. But, the guy who bored the cylinder the second time did pressure test it after he put the Engine back together. Not sure of his procedure or what the actual number was, but he told me that it was all good. Things could have changed over the past year I suppose. However, an unmetered air leak should cause a lean condition and I really believe that my issue is too much fuel or not enough air in the problem throttle range.

I do not have access to another carb without buying another one. Small possibility that there could be an issue with the airstriker, but very slim. It is a brand new unit. Not sure what the last guy did to the stock carb, but no matter how small of a main jet I put in it, it ran pig rich. I even blocked off the fuel enrichment circuit completely to rule out the choke as an issue. Nothing helped. I think something was done internally to it. She would blow smoke like a freight train and go about 2 MPH. I only found out that it was junk by cutting the fuel supply and letting the carb drain the float bowl. The machine would finally pickup speed and power when the carb was almost out of fuel. That is when I switched to the new carb, and all of those issues went away. So I parted out the stocker and scrapped the body. I have no backup.

As fas as EGT and CHT measurement, CHT is measured via a plug sensor, and EGT is measured by a probe in the exhaust just past the first elbow after the exhaust manifold. Maybe not super accurate, but a decent picture of what is going on.

I have not performed a fuel volume test. Didn't see it as necessary being that the pump is new, and the return line is always full. I will do this test to rule it out. The tank is clean, had it clean and coated by a radiator shop. The fuel filter is always clean as well.

The airbox I put together could be a problem, at least where the issue lies. I will post some pics of this later when I get a few minutes. It could be starved for air under a heavy load. However, I can't run it with the lid open because it runs so lean at low revs that I can't even get past 1/4 throttle. I do need to dig into this. Maybe I will attach a rope to the lid so I can open it above half throttle and see what happens.

I really believe my problem is rich vs lean. I have not done a plug chop per se, but I have put a new plug in every time I have changed jetting. I check the plug after every run and it is always black with carbon on the electrode.

Sorry for the extensively wordy reply, but I'm trying to give everyone as much info as possible.

Just my opinion but having to rig the air box to get it to run means it is lean throughout rpms and you're lid modification is making up for it.
Air leak or fuel delivery is where I would start. Lean across the rpms is generally more than jetting unless u are way off and you seem to be in the ball park.

Is it making a spy hunter smoke screen with the 155 main jet? Pwk35 is close to stock pilot carb and they run mid 140 mains on stock Engine and stock exhaust. Intake considering. Don’t pop your Engine I’m just saying. My pilot would not run well at all with a 155 but then the 152 main was perfect. If it’s a lean bog there’s a problem and that’s one thing; if it’s not clearing out and smoking like hell then you may be slightly over jetted. How’s plugs look?

Could be weak ignitio too. Is the cutting out softly or violently? Violent would be ignition, soft more likely fueling

Just had another brain fart.
bugeye59 mentioned the homemade air box you made. FloridaEdd also commented.
We need a pic of that air box as well as a pic of everything bolted together. I need a clear pic of the carb.
I am really grabbing at straws now but I wonder if your homemade air box has put a steep angle on the carb. If it did then there is a possibility that your floats are at a steep angle and the fuel level in the float bowl is all wrong. You said it wasn't leaking fuel out the carb but you may have a real high fuel level.
Pics please.

This right here may be something to go on. Never considered this, but I can see how even a few millimeter change in angle could gum things up now that you bring it up. The airbox I fashioned is roughly a re-creation of the factory one, and mounted in exactly the same way. Although it is plausible that the intake tube could be tugging on the carb making it off kilter due to slightly different geometry. I will get some better pics today in the light. All I got was some crappy ones last night in my poorly lit garage. Will post later today.

Zero...No smoke screen throughout the range where I'm able to run the machine. Not sure if it's super smoky when it starts bogging above 1/2 throttle. I don't have eyes in the back of my head unfortunately. I'm gonna slap my gopro back there, make a run and see. Interesting info on the jetting, but when I tried running on the #152 main the machine wouldn't even get over 40 MPH and just felt bad. Suppose it could be relative though if I have a problem like what canadian oddy mentioned. The plug always has carbon on the electrode (which is what leads me to believe I have a rich condition where my problem lies), but at least the plug is no longer wet with fuel on the #155 main. 99% sure its not ignition related. I'm using a brand new ignition coil and a CDI (Capacitor Discharge Ignition) unit from a known well running machine. I've done all the tests on the alternator, pulse generator, rectifier etc... The spark looks just as strong when testing recoil vs electric start. All check out.

I might get hell here for saying this but just take the air box off all together and run it without for a test. Put a piece of flyscreen over the end of the carb and make a run on pavement -- not a dirt road. That will tell you for sure if it is the air box or not. Make a mental note of how the carb sits with and without the air box. This will probably be the easiest solution to the question.

Personally I am now leaning toward a bad carb you probably got off feebay.
That's why I asked earlier if you had another carb for a test. I feel this way because you have close to required jetting and your plugs are black as coal. Then when you open it up it floods. Even a few degrees on the carb angle will not kill your Engine like you describe. You have checked almost everything and it don't run. These machines are simple. All you need is fuel - air - and spark. You have all of the above. If the spark timing was off it would not even start or would backfire. Air is air and you got that or it wouldn't even run. That leaves fuel, the most complicated issue on these machines. If the fuel pump puts out your good on that. That only leaves one more thing ------- the carb and it's adjustments.

Point taken. I definitely cannot rule out the carb being bad. Although, I did purchase it brand new from a reputable seller, and the carb was sealed in factory packaging when it arrived. I suppose there is always the possibility of getting a lemon with any mechanical device. Unfortunately this would be expensive to test as I would have to buy another one to be sure.

Here are a few pics of the airbox setup and carb. Don't know if the pic of the carb is of any help. You all know how buried it is down there. The airbox itself is a waterproof dive box measuring aprox~ 9"L x 7"H x 7"D
And in case anyone is wondering why I painted the machine Kawasaki colors...I own a roofing company and my company's colors are lime green on black. The oddy matches my truck and looks sweet on the trailer behind it. I'm a nerd, so what.

Well I'm glad I asked about your DIY airbox and pics because I see fundamental flaws.The filter foam sheet you use is ONLY being utilised and CONCENTRATED at the carb inlet hole.Its not supported away from the hole and surely just compresses while it gets sucked down and compresses against your wire gauze.Secondly the small gauze is taking up robbing your small hole...starving for air more and more relative to throttle demands.Also your upper duct has a big loop in it comming down into your airbox hindering straightline air pull.How big is the gauze hole? Try running it with the foam out.That will see if the foam is compressing shut.Your gauze as well is taking up too much surface area.

OH MY
That what I see to.
The other thing I see is that foam seems to be from a foamy mattress. I don't think that stuff is pourous enough.
Like bugeye said run it without the foam for a test.

From what I see there, I don't feel you need a filter inside that box. You have your filter up high at the end of the snorkel. If you look at the stock oddy set up it has an air box up high on the end of the hose where you have your filter. Then it has the foam filter inside the air box above the carb. This filter is supported by a cage to keep it off the carb inlet hole. You are choking your air flow off to the carb with that second filter you have laying over the hole.

By the way very nice job on that air box.