Slurve98

I'm having an issue with acceleration when I'm at 70 mph. I can bottom out the throttle and the engine bogs down. I've checked the air, gas and spark plugs. What am I not looking at?

Easy Rider 2

What / how exactly did you "check" ?? You probably are looking at the problem in one of those areas.

If it's been a long time since the air filter was changed, do that.
Ditto the plugs.

Also check for loose clamps on the air box and around the carb(s).

Then give it a good dose of Berryman's B12 Chemtool and take some short rides over a couple of days.

Things get a good bit more complicated after that.

__________________
My Rides:
'07 Honda Shadow VLX 600
'06 Suzuki S-50 (VS800)

The_AirHawk

What have you done to the bike, recently? Any "snorkelectomy" or other airbox-mods, exhaust mods, etc.?

The bike is "going lean on top". If it used to rev-out, and you have not changed anything, one of the things ER2 has pointed-out is the problem.

__________________
Parfois, on fait pas semblant
Sometimes, it's not pretend
Oderint Dum Metuant
Let them hate so long as they fear
политики предпочитают безоружных крестьян
Politicians Prefer Unarmed Peasants
Nothing to see here, Citizen. Move along now...

Slurve98

Thanks for the input ER2 and Airhawk. I've removed the air filter and gone for a ride - no improvement. Performed the Clymer manual test on the fuel system - it's a pass. It seems to be a vacuum or ignition advance problem but I'm not able to isolate. I can get the bike to accelerate if I give it gas then back off, then give it gas and so on until I get the speed I want. There is no punch if I have to pass.

Easy Rider 2

I don't think either of us recommended that you do THAT.

How about addressing some of the things that we DID pose ??

Does it have a stock air filter or something like a K&N ??

__________________
My Rides:
'07 Honda Shadow VLX 600
'06 Suzuki S-50 (VS800)

Slurve98

The bike is stock, no mods. Done the Berryman thing to no avail. Spark plugs are new. The things I did were at the local honda shop advice. The clamp on the carbs to head are secure. The bike has punch at less lower speeds, it's lost the punch at the higher speeds.

The_AirHawk

Sounds like you still have a vacuum-leak; the slides in the carbs are not opening-fully. Could even be caused by a torn/holed slide-diaphragm.

Ignition-advance for the waste-spark CDI is a preprogrammed curve, and is rpm-dependant. No vacuum or mechanical advance.

TEH EDITZ:

One thing I thought of - how "free" is the exhaust? If you've just brought the bike out of storage, did you check for an animal/nest in the exhaust? It will probably be in the plenum, rather than the silencer. That could most-certainly choke-off the bike at higher rpm's. A wire coathanger stabbed-down the end of it to check could be useful.

__________________
Parfois, on fait pas semblant
Sometimes, it's not pretend
Oderint Dum Metuant
Let them hate so long as they fear
политики предпочитают безоружных крестьян
Politicians Prefer Unarmed Peasants
Nothing to see here, Citizen. Move along now...

seruzawa

It sounds like the accelerator pump is not working.

__________________
"Make no mistake, Communism lost a big argument - one we know today as the 20th century."