No Power 5th Gear

[Megadan]

Originally Posted by kyriakos

Also dropped a 120 main jet in, ran carb cleaner through all jets, everything seems clear for intake. The 120 jet didn't really have an effect either.

This little detail right here catches my interest. That is a big jump in jet size. A 120 main on a Hawk with a stock exhaust system should be bogging out pretty badly, almost to the point of cutting out. That and taking the air filter off - aka open carb, also had no measurable or audible change - also odd.

The fact that there was zero change leads me to one of two conclusions, especially considering all of the testing, checking, and setup you just described.

The most likely conclusion in my mind is something is definitely wrong with the carb.

Either the bowl is barely getting any fuel to it - float level is too low or the valve is not opening fully, the Petcock isn't flowing enough due to some sort of blockage (not likely, but I won't discount it). If you have a fuel filter added to the fuel line, it may not be able to flow enough to keep up at wider throttle positions and is starving the bowl.

There is also the chance that you have a vacuum leak at the intake to head flange O-ring or Carb to intake O-ring. Or a poor seal at the throttle slide cap (also an O-ring seal).

The pictures of your spark plug (and the sound of your engine on the top end in the video) after that ride definitely back up something causing a lean condition. I would avoid pushing it hard for very long as you may cause damage to the piston and cylinder body.

If it were me, I would swap over to the Mikuni clone and call it a day. However, I would also check both O-ring seals on the intake for any sort of damage. It's not unheard of for the O-rings to be damaged during assembly at the factory.

Also make sure you don't over tighten the intake bolts to the head. Less than 20ft-lbs (about 15-18) is all they need. Too tight and the aluminum flange on the intake pipe can distort and actually cause a poor seal.

[lefty]

Please Forgive this inquery, Most of us have at least once had the Choke in the Wrong position. This happened to my this week! So is the lever all the way down? Is it functioning correctly?

Best, Lefty

2015 Hawk 250
2006 883 Sportster
1972 Honda CT70
Lost along the way;
1982 GS1100L
1983 Honda 185s 2ea.
1974 Puch 175mx
Right Arm

[kyriakos]

Originally Posted by lefty

Please Forgive this inquery, Most of us have at least once had the Choke in the Wrong position. This happened to my this week! So is the lever all the way down? Is it functioning correctly?

Best, Lefty

2015 Hawk 250
2006 883 Sportster
1972 Honda CT70
Lost along the way;
1982 GS1100L
1983 Honda 185s 2ea.
1974 Puch 175mx
Right Arm

Yes, choke is functioning correctly, and down while riding. There was also an O-Ring at fuel sensor on bottom of gas tank that leaked, but has been replaced. I thought maybe a piece of that ended up clogging the petcock. A few days ago, I took off the petcock and ran carb cleaner through it, and the flow seems good. I had worked on a moped with a bad gas cap vent, so I ran without that cap on; but still no improvement.

I can't say there's no 'audible' sound when going WoT, I can hear the engine noise 'get deeper' between half and WoT, but no noticeable improvement in power. Makes sense that the sound would be air getting sucked without more fuel.

I'll pick up an O-Ring kit on way home and swap those out from carb and intake. The rings from factory on carb>intake and in the bowl seem to be stretched/tad too big.

Come on USPS, here's to the new carb/exhaust!

[JerryHawk250]

It wouldn't surprise me that once you replace the exhaust it will be a whole new animal. The cat could be plugged up just enough to rob it of power. It's probably something simple. Looks like you ruled out most of everything else.

[Weldangrind]

I've had two CG motors where the o-ring wouldn't seal where the intake tube meets the head. This caused a symptom where if you revved the engine, it would take several seconds to calm down to idle. On one of them, the o-ring was simply not inserted into the groove properly. On the other, the groove was cut too deep, resulting in no seal at all. I stacked two o-rings in the grove and called it a win.
None of this sounds like the symptoms you're seeing. I agree that the next step is the carb and exhaust.

[blanc12]

Is the throttle lifting the plunger all the way in the carb? Just a thought. Could be stuck or adjustment may be off.

[kyriakos]

Plunger confirmed to travel completely.

A slight update; my exhaust came in a day early. It sounds much more mean, but still no change in top speed on my quick test ride.

Hoping carb makes it tomorrow or Saturday. I can't wait to feel this beast, now that it's modded much more quickly than I had planned to do. Expecting a 15-20 mph jump when we knock out whatever this issue is!

[Its_not_a_honda]

Just thought I would show this. I am in the process of changing my carb and noticed this when reassembling. I have an Apollo 250. Different style engine than yours but you might want to check this. Intake gasket. One way perfect. The other way big blockage.

[JerryHawk250]

Originally Posted by kyriakos

Plunger confirmed to travel completely.

A slight update; my exhaust came in a day early. It sounds much more mean, but still no change in top speed on my quick test ride.

Hoping carb makes it tomorrow or Saturday. I can't wait to feel this beast, now that it's modded much more quickly than I had planned to do. Expecting a 15-20 mph jump when we knock out whatever this issue is!

Hopefully the new carb will resolve the issue.

[Megadan]

Originally Posted by kyriakos

Yes, choke is functioning correctly, and down while riding.

Your choice of wording here interests me.

On the Stock Keihin style carb, the choke should be all the way UP while riding, with all the way down being fully engaged.

The Mikuni carbs work opposite of this, all the way down being choke off, and all the way up being engaged.

[JerryHawk250]

Originally Posted by Megadan

Your choice of wording here interests me.

On the Stock Keihin style carb, the choke should be all the way UP while riding, with all the way down being fully engaged.

The Mikuni carbs work opposite of this, all the way down being choke off, and all the way up being engaged.

On the stock PZ30 the chock is off all the way down.

[Megadan]

Originally Posted by JerryHawk250

On the stock PZ30 the chock is off all the way down.

I actually had to go dig mine out of it's storage box to confirm lol. Been so long since I even looked at it that I forgot."

Never mind, ignore everything I just said.

[kyriakos]

Argh. New carb on, exact same behavior with power and speed. Maybe it is something electrical... Not sure where to start with that though...

[franque]

Did you check the intake to see if the gasket was partially blocking the port? I'd also do a leakdown test, too. You can swap CDIs pretty cheaply, maybe it's a bum CDI.

[Megadan]

I would like to change the line of thinking here and instead of focusing on top speed in 5th gear, maybe look at engine performance in other gears based on RPM.

Does the bike pull hard through the full RPM range in 2, 3 or 4? Does it feel like the engine falls off a bit in the higher RPM range when going through those gears too? It may be a little less pronounced because the load on the engine is lower, but it should be something you can still feel. The engine should pull nice and strong all the way to at least 7000-7500rpm.

I am still curious if you checked the O-rings on the intake pipe between it and the cylinder head. I would also look over the rubber on the intake pipe itself to make 100% sure there is no hole, tear, or crack that may be causing a vacuum leak. It's not unheard of even on a new bike.

Beyond that, assuming everything on the engine is good, then we need to look at other things that can be causing enough drag to slow the bike down.

Have you checked the rear wheel bearings? The 2017's seemed to have a problem with the factory installed bearings being installed poorly and were locked up and almost impossible to turn. My own bike had this issue.

How much slack is in the chain? If the chain is a bit too tight it will also cause some drag. I have found that to get proper chain tension on my Hawk, with the swing arm at full droop you need around 28mm (A bit more than 1 inch) of free play at the center of the chain - or 15mm with the suspension compressed until the chain is at it's tightest.

Have you checked the rear brake adjustment? It's not uncommon for some of these bikes to come with the rear brake adjustment just a hair too tight. This causes the rear brake to drag, which in the case of the Hawk is quite a lot of braking force since the rear brake is rather overpowered.