84 spree bbk - goin' GROOVY

[wite_rabit]

I just wrote a nifty post on my "smart" phone and lost the whole shebang. I will cut to the chase!

After my bbk is installed and operable I aim to test out Somender Singh's grooved combustion chamber. The story goes that a groove (or four for an nq50 head I think) improves flame propagation and efficiency. Cooler temps, leaner toleration, higher compression without detonation...

Bear, feel free to weigh in! I won't link externally in my first post after lurking for months so google it if you care to. Chasing that stock spree power after melting my own piston off-idle coasting downhill... I didn't lurk long enough!

[wite_rabit]

Head dremel'd, turns out though the new 48mm kit didn't need it! The piston doesn't travel that far when cold - maybe when things heat up though. My compression appears good but the battery is pretty dead. I long for a kick start conversion!

[wite_rabit]

Compression tested with jumpers (car engine off) at 150psi throttle open. Got it started and crawled around the block, barely any throttle. Seems idling is a frequent recommendation for break in... Shoot. I wanted to charge my battery! I mosey'd over to the gas station and am loitering while my little scoot cools.

This bbk sounds really neat! On the subject of grooving the head, mine only appeared to have deposits behind the electrode (guessing) - one groove might be enough provided they are even effective on these little bores... How long does a striker crank drive the piston? There seems to be plenty of clearance on the 48mm Taz bbk.

[ClemSpree]

Frequent idling is probably the worst for breakin on an AC motor, IMHO. Run it lightly, varying speeds, increasing demands, varying speed. Let it cool down and repeat a few times, it shouldn't take long.

How much breaking do you think joe schmo gives to his weedeater, most of them seem to die bc of carb issues or running w/o premix rather than "breakin" issues.

[wite_rabit]

Excellent! I have run a few slow runs 10-20 minutes, thus far my only problem (after jumping) was fouling my plug. Well that and killing the battery trying to start with a fouled plug! I have some 4s on order while I'm at work, I will gap and install and hope for a jump start tonight.

Sb50 reed block is sitting a few miles away with my jet kit - hopefully the right size! Older threads all mention holes/no holes in the Taz bbk... Should I toss a breather onto my carb to bypass air box? It sure seems to be getting capital P plenty of gas.

[paulpauly7]

with a stock crab and a open air filter the pilot jet will run lean oh and you cant change the pilot jet only the main .Also you want a 8 plug not a 4

[wite_rabit]

Shoot. Guy at the counter said it would help limit fouling during break-in. Maybe tomorrow I will track down an 8! My engine won't blow up using a 4, right?

[wite_rabit]

I wonder if I overheated today due to running the 4. In any event two things lead me to believe I am running rich, beyond the fouled plug: the bike ran like a CHAMP - as it was running out of gas. Further, pulling up a corner of my air box lead to incredible acceleration and top speed gains compared with putting around at 15mph WOT. Fuel economy stunk too!

I want to groove out right now, but first I will set idle and needle position. Then jetting correctly. Then port my intake to an sb50 reed and establish a baseline... THEN groove to compare. A free flow might work much better with grooves idling alongside the stock pilot jet... Provided this stuff is sound!

[paulpauly7]

what is this groove your talking about

[wite_rabit]

In my quest to learn a bit about cylinder heads before biting the bullet and dremeling my 41mm head to 48 to match bore, I stumbled across articles about Somender Singh. This guy tested various modifications to heads aimed at improving combustion.

The groove is a channel cut going from the chamber into the squish band. It is said to increase turbulence within the chamber resulting in a more complete (and snappy) burn. Efficiency goes up and more gas burns. Supposedly the engine runs cooler, can tolerate more compression without detonation, and even leaner conditions without spiking heat.

It is nothing more than a 45┬░ groove channeling combustion chamber into squish band. I noticed an area of sooty blackness on my head (presumably begind the plug electrode) which will eventually be my groove target! Each groove reduces compression slightly though, so a milled head is an ideal candidate for multiple grooves. You ever see home improvement? More power ho ho ho

[wite_rabit]

Well! Off roading months ago, which splashed battery acid around leading to frayed wiring, also caused my voltage regulator to fall off. Just fell off the other day... I will Jerry rig something and possibly toss on my larger reed block after down jetting some. If anyone sees this and has experience swapping gears without a huge press feel free to chime in! I know I saw a post or two here about it...

[paulpauly7]

spree gears dont need pressing theres only 2 gears in there.

[wite_rabit]

Oh thank goodness. I hadn't cracked it open (anxiety is a - and I have my second son due any day now) so I'm glad to hear it! Unfortunately my jet kit was not right for my stock carb. Rich as the * unless I wedge something into my air box cover, but then it comes alive. Blew my tube, too. SOON I SHALL GROOVE.

[patthesoundguy]

You shouldn't have to mess with the squish band on the head the 84 head is already the same as a custom high compression head for the most part. Just shave it a few thousands to raise the compression possibly. Unless you have a lathe to cut the head and the right dimensions to follow. Did you drill the holes in the air box like the instructions said to. If not that's why it was rich not enough air to feed the larger displacement. You can just replace the airbox with an aftermarket air filter.

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[patthesoundguy]

Frequent idling is probably the worst for breakin on an AC motor, IMHO. Run it lightly, varying speeds, increasing demands, varying speed. Let it cool down and repeat a few times, it shouldn't take long.

How much breaking do you think joe schmo gives to his weedeater, most of them seem to die bc of carb issues or running w/o premix rather than "breakin" issues.

You don't ride on a weedeater and a weed eater breaks in real quick because it only has an aluminum cylinder.

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