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Hornsmith 13th June 2019 07:17

Blast Project (and will be needing help most likely)
Hello all! I've been using this forum for ages now, lookin up what I need to know, but this is my first post! Reason being my Blast kind of, well, died. Also, I'm building it up to something which will be most likely astounding, whether good or bad.
But about the dead engine. It happened a while back, right after I got it actually. I had been testing it out, making sure all was with with it, and it occasionally made this loud banging noise accompanied with the bike suddenly jolting. Not so great I reckoned but still rode it a wee bit to try and figure out what was going on.
Well, one day, just as I was rolling down the steep hill that I live on, it made that clack sound, and then died. It wasn't a sudden smack and dead engine, but more like smack and then it just petered off and died. Needless to say, I couldn't get it started and ended up getting my triplet older brothers to help me push the thing back up the hill to my house. That's a grand story on its own, but back to the topic.
That was a little while back, and since then I have put in a good amount of time on the engine. As I speak, I have tore down the engine (my first time may I add) and found an obvious culprit. The exhaust pushrod is hella bent.
The pushrod is not difficult nor expensive to replace, but the concern is more what caused it, eh.
I don't see anything obviously wrong with anything else.

A probable cause may be related to the cylinder, which is an NRHS 515 big bore kit with a higher comp piston. I would reckon that there's less space between this piston and the valves than there would be with a stock piston, and thus could have banged it? However, the valves look fine, definitely not bent or nothin, so not sure. Additionally, were that the cause, wouldn't it be smacking every time the valve opened?

Either way, I'm determined to make this thing work, and plan to be doing a whole lot more to it. I just put in a bronze oil pump drive gear, and I'm waiting on a Buell Ulysses Swingarm and XB wheel which will replace the stock. A fun thing to note is that all the XB swingarms will bolt on, though there is some trouble with the shock. To be solving that, I'm going to push the boundaries of laziness, with a (maybe) genius solution.
The Buell Blast shock is pretty short, and has eyelets on both the frame and swingarm mounts. The XB shocks have a clevis joint on the swingarm side, so you can't use the blast shock. Additionally, the XB shocks are way too long to fit, properly, so you can stuff one of them in.
However, the Buell XB long frame models (XB12x, XB12ss, XB12STT) have a slightly longer swingarm, and a much farther away swingarm shock mount. Probably not so far away that a normal XB shock will work, but maybe, just maybe, the shorter Buell XB12scg shock will fit. I'll probably need to cut away space in the Buell battery tray area, to make up for the shock being at a farther angle, but that's super simple. I mean hey, maybe it won't work, but I guess I'll see.
I've got a ton of other things I may be doing (including modifying/fabbing a new gas tank, making a new seat, chopping the tail, doing something about those blasted peg mounts, and making luggage)
Anywho, tell me what you think of my wild thoughts, any advice will be much appreciated as I have basically no experience at all with engine work until now (actually I've done a fair bit of work on my ol' honda rat but that's mostly simple stuff, like carburetors and good ol' electrical tape intake leak seals)
Photos will be coming

Hornsmith 13th June 2019 07:48

I just remembered a bunch of more stuff I've done/will do. I've got a sportster carb with an accelerator pump that I've got mostly dialed in already on, I swapped out the ugly airbox for a velocity stack, that will be needing some filtering, I'm gonna change the ignition (partly because the new carb doesn't have provisions for the sensor), I'm gonna doing some bodywork on the front, might be changing headlights, will be making a new muffler (currently has a very battered V&Hines, and I will be using the V&H header) and something with the shifter but I haven't decided what yet
Anyways, back to my current hangup, the not working engine.
The exhaust pushrod is severely bent, and I'm thinking I should find out how that happened before sticking in a fresh one (Click for link to photo). It has a NRHS 515 piston, which may be related, and it was making an occasionally sudden clacking noise before it died. Any things I should specifically check?

rokytnji 13th June 2019 18:47

Do you have the tools to look down the spark plug hole for any hit piston marks?

Hornsmith 13th June 2019 21:38

Thanks for the tip. I actually have the whole cylinder and head removed at the moment, and I've got pics of the valves and piston face in this link. They look fine to me, but I suppose I could be wrong :dunno

sportsterpaul 13th June 2019 23:49

Tappet didn’t seize up did it?

Hornsmith 14th June 2019 00:50

I just checked that, and they're moving freely. I'm wondering if maybe the valves themselves are stuck? I'll be doing some more investigating tonight. Is it possible that I should simply put some new pushrods in, and all will be well? I mean, that would be easy, but I'd rather not just break a new pushrod, eh

sportsterpaul 14th June 2019 02:40

Something happened, no doubt, they’re must be evidence of some kind somewhere? A bent pushrod is pretty telling.

Hornsmith 14th June 2019 06:06

That's what I'm thinking, but I don't see anything obviously wrong. Lifters move freely, valves look fine, the piston and crank move. As I said, I don't have any experience working with evolution motors.
One thing that I am curious of though:
When I'm spinning primary and all that, it seems to move in a jumpy fashion, not continuous but more like with several points like it moves, stops, moves, stops. It's not rough and doesn't make any scratching sounds, but it doesn't move in a smooth continuous fashion. Is that normal?

rokytnji 14th June 2019 14:11

Flywheel and clutches engaged and spark plugs removed sounds like what you are describing.
That or a worn primary chain or worn clutch basket or compensating sprocket teeth maybe.

Hard to say without a video. from youtube like I made showing mine running after reassembly.

No hit mark on Piston? Weird. Push rods don't bend on their own. Check rockers for bind points I guess.
Look for a hit mark on rocker cover maybe.
To get this straight.

This ran OK and no valve adjustments made by you before valve was bent.

Flame__ 14th June 2019 14:47

Valve springs? As for the move stops thing, IDK. Did you check up and down play on the connecting rods?

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