Blast is SLOW. What else to check?

[pierce]

Sweet - it seems like everyone I have ever known that owns a superbike does that too. I think they just don't know how to shift - glorified scooter. I think its also a prerequisite if you own one that you either wear shorts and flip flops, or in a power ranger outfit. I love that crowd.

http://www.youtube.com/watch?v=q0YkXmebAGM

Best thing about that crowd is as soon as it hits 74 they get cold and you won't see them until next year.

[adam728]

Slabber - compression check will be done, if I can ever find the right adaptor for my gauge! I pulled the plug and got out the gauge the other day in order to check it, but failed. 14 mm end doesn't fit well in a 12 mm plug thread. Maybe a big hammer..... :p

pierce - Not shifting it wrong. I've tried short shifting, stretching a gear out, etc. I've tried to carry 3rd pretty high to see if I was shifting too soon and missing some magical power bubble up high, but by 60 mph acceleration was dropping off, and I saw no reason to abuse it more just to look for a limiter. When hammering on it I go 2->3 at about 35 mph, and 3->4 at about 50->53 mph.

RuiP - No need for an XP9. Just trying to get my sister's little bike sorted out for her. As i said earlier, she laughed when I told her about this, then said she's never been to 60 mph on it yet.

[brumbear]

Can you data log a blast? I am sorry I never worked on one and don't even know what set up they have. It seems it's flattening the power curve to soon? If it runs strong up to a certain point you can rule out compression more than probably. Valve float? I would honestly lean towards a simple carb malfunction if a blast has one. An ign module malfunction is doubtful but mapping or tps out of parameter is possible I would lean towards timing advance if it's flatening out and there is no fuel delivery problem. Not to be a douche but the fuel filter is clean yes?

[turboraven]

Simple..it needs an xb12 motor.

[pierce]

Theres one problem, you would get more power by pushing straight up to the limiter. After all, the limiter won't hurt anything and I often recommend to new blast owners that they should find it in each gear. 2 -> 3 at 35 is going to be lugging the blast engine. You should shift as such:

1 -> 2 around 30 (just before)
2 - > 3 around 50 (etc)
3 - > 4 around 60
4 - - > 80

The powerband for these engine is is the upper rpm, 3500 - 6500. With your shifting the engine would be allways sitting below (and lugging) and working really hard. Shifting prematurely just kills all the power on these bikes. Contrary to what most think, the blasts love the upper rpm and want to be screaming. NEVER shift into second before 30, doing so can hurt the engine.

Hang around the blast forum you will hear riding the limiter a lot. For example J-Lee rides the limiter in 5th around 111 (he got a ticket - sad face) and he can get their really quickly. He also has a video of him showing the accel from stop light to 80 and it takes maybe 6 seconds.

With significant engine work and the SE programmable ignition my limiter is pushed to 8K so I rarely hit the limiter (shift to second around 45, third 60, 4th 80 and I dont go beyond 100 so never hit fifth.) On the on ramp to the freeway I could probably hit triple digits. However, I don't ride it as much as I used to as it has so much customization I use it as my show bike. Its a lot of fun though.

[GAXB9R]

So slow might be normal.

Probably so wouldn't you think...

[adam728]

Theres one problem, you would get more power by pushing straight up to the limiter. After all, the limiter won't hurt anything and I often recommend to new blast owners that they should find it in each gear. 2 -> 3 at 35 is going to be lugging the blast engine. You should shift as such:

1 -> 2 around 30 (just before)
2 - > 3 around 50 (etc)
3 - > 4 around 60
4 - - > 80

The powerband for these engine is is the upper rpm, 3500 - 6500. With your shifting the engine would be allways sitting below (and lugging) and working really hard. Shifting prematurely just kills all the power on these bikes. Contrary to what most think, the blasts love the upper rpm and want to be screaming. NEVER shift into second before 30, doing so can hurt the engine.

Maybe I need to look into timing as well. I can say for certian in 3rd acceleration is hardest below 55 mph. Carry it over that and by 60 mph it's almost stopped pulling. Is the rev limiter a hard limiter that is easily audible, or a soft limiter that cuts spark in a way that you don't really notice? (we make some ignitions that cuts spark, say, ever 6th revalution, then 5th, 4th, etc, so that power tapers off and you don't feel like you are hammering a limiter). This bike feels like anything but a rever, it pulls quite hard in the midrange, then signs off gently. 3rd pulls very well from 40ish to 55.


Please explain to me how shifting to 2nd before 30 will hurt then engine. Is my sister supposed to roll thru her neighborhood in 1st making all sorts of obnoxious racket in 1st?

[jetlee]

The rev limiter is a soft limiter; it's a spark-skip limiter. If you hit it too hard, you flood the engine (as it's not burning fuel while it skips spark) and it acts like a complete ignition cut until the engine slows way down (pull clutch to drop the rpms fast while keeping the bike under control). If you hit it softly, it's easily audible. It doesn't pitch you forward or anything like that, just stops accelerating.

I used to cruise on the limiter when I had stock ignition. This Ultima has a wicked-sounding spark-skip limiter though.

Shifting too soon is putting a lot of pounding force on the bearing journals. The piston is moving slower and your hammering on it with each combustion. When at higher rpms, the piston is already moving faster so the force transmitted to the journals is less.

Think of it like this: hold a brick in your hand tightly, hit it with a hammer as hard as you can. Hurts don't it? Now, do the same thing, but loosen your grip on the brick so it's already moving a little when you hit it. Doesn't hurt as much, right? Think of the brick as the piston, the hammer as the combustion and your hand as the journals.

[jetlee]

...and just for shi-grins, I went WOT from 60-65 in 5th this morning. Even with all my mods, it still took me 5-6 seconds.

I rarely run in 5th below 70mph. In stock form, 4th hits the limiter at about 80mph.

The limiter does not hurt the bike. I shifted at the limiter so often it was ridiculous. Hit it, see what it feels like.

Check your air filter and drill a 2nd hole in the exhaust opposite the first (stock) one.

[adam728]

I understand not lugging it and hammering bearings. I don't understand how running nearly 3,500 rpm in 2nd is "lugging" this bike. Seriously, am I supposed to tell my sister to never upshift until at redline? Heck, look at Buell's suggested shift points (for cruising, I assume).




The hammer/brick analogy isn't quite right. You'd be hitting the brick faster at higher rpms, not holding it looser. Unless the bearings somehow become elastic. Not that I can think of a better example, but I do know what you were trying to get at.

By the way, nothing to drill in the exhaust, it's a Vance & Hines (stated in 1st post).