Blaster with no response

[tfaith08]

So I recently rebuilt my wife's Blaster. I did a moderate port (mostly port cleanup), kept the FMF exhaust and UNI filter, stock carb, reeds, head (decked just a bit).

It passed the leak down test both when assembled and a few days ago, carb is clean and in great shape, pipe is free and mounts up good, filter is clean, jetted correctly and double checked by a Honda tech/friend, stator is strong, compression is 132, plug chop was perfect (cardboard), but response is dead and it struggles to rev.

This problem has gotten much worse over the past few weeks. Originally, it pulled like a champ and ran as smooth as an electric motor.

Now, it revs like it's under load when it's in idle and only barely gets better when it's been warmed up AND ridden for a minute or so. It kind of 4 strokes when it revs and pops a bit when it's approaching the powerband. The situation persists from less that 1/4 throttle to WOT. On very top, it acts like it's missing as though the plug is blowing out, but closing the plug gap to .015 made no difference. On top, it's very, very bad and strained. It really only runs well when it's below 50 degrees outside.

Jetting is 270 (remember, my porting is more along the lines of a port cleanup), stock needle in second from bottom position, stock pilot, AS @ 1 3/4 out with FMF, 40:1 yamalube, UNI w/o airbox.

I'm at a loss.

 

[Awk08]

float height ?
brass washer under main jet ?
reeds good ?
ground @ coil clean/bare metal ?
stock stator ? ohms out to spec ?
1-3/4 AS = highest idle ?
filters directly on the carb have been known to cause jetting headaches

running better @ colder temps suggests a rich jetting condition

unless you're at sea level, middle clip position on stock needle should be good,
@ 40:1 fuel/oil both the needle and that 270 main may be fuel/air ratio rich,
most jetting info on here is based on 32:1 ratio and that 270 should be close

 

[tfaith08]

IDR float height, but I set it to factory spec when I built it.
Brass washer is there.
Reeds check out.
Ground... Hmm.
Stator is good.
1-3/4 AS = perfect
Stock inlet tract, stock filter location.

I did tune it when it was in the 40s outside... Now, 90+ is the norm. Why did I overlook that?

We're at 140' above sea level. I'll try the middle position and see if that helps. We just got back from a big ride today (minus the Blaster).

*I highlight things that I intend to come back and read later*

 

[Awk08]

I'll try the middle position and see if that helps. We just got back from a big ride today (minus the Blaster).

needle = 1/4 throttle to 3/4 throttle and will effect the main jetting also....exactly where you're having troubles.
check the plug wire per the manual

IDR FLOAT HEIGHT ?

highlighted for fun

 

[tfaith08]

Lol, I set the float height to whatever factory spec is, but I don't recall what it was.

 

[98blaster]

Wow pretty colors lol

 

[98blaster]

I had a very similar issue last summer, bike would run but felt flat and had hard time revving out some times would break up up top,my stator ohmed out to specs, so fought with carb an thinking it was a tuning issue but could never get it, I swapped stator from my other bike an BAM fixed

 

[tfaith08]

Issue solved! There was an airleak between the carb and boot that didn't show up on the leakdown test.

When I assembled it, I grabbed the wrong clamp for the boot and it was tightened all the way and it still didn't provide a sufficient seal. I overlooked it because I was tired and it was almost midnight. After some time, the leak started to get worse which presented as low power and trouble revving. I found it with a can of carb cleaner. Originally, I had a 280 main, which I mistakenly listed as a 270 in the first post my brief rebuild thread. I fixed the problem and gave it a go and it was night and day better. I went to a 270 main, cleaned the filter, switched the plug, reset my idle screw to 2 turns out and let it rip. Absolutely perfect jetting the first time. I'm either getting really good with this or I got lucky lol.

Man is this thing awesome. I forgot how fast it was when I first got it together before it started acting up. Stabbing the throttle from idling along in 2nd will result in the ass end dragging the ground in an instant. 4th gear tire lifts are effortless. Playing in the wet grass is amazing lol. I was cutting donuts while sitting on the seat in 5th gear. If I leaned off the side and far forward, I could get it to break loose in 6th.

Slinging the back end all the way around at 30mph is quite a rush, but incredibly worth it once you pull it off without flipping. What saved me was that I was leaned all the way over the non-pipe side with my foot on the front of the peg and the back of my knee on the gas tank. All the while, the engine is screaming for it's life and I never backed out of it.