Author Topic: ohh dear...spark plug shoots out of cyl #2....do i need a new engine??? (Read 6326 times)

Andrew Foss · « **on:** May 28, 2006, 12:53:25 PM »

just like the title says...i was running fine today, went to take off at a stoplight and BAM! i hear the exhaust leaking from what i though was the header after a loud backfire-ish sound, and when i looked down, the plug was hanging on the wire (still sparking). i tried to put it back in but it just turns forever....does this mean i need to replace the top end, or can i cut new threads into the head???
-andrew
PS-the bike is a 76 cb750f

JonnyHonda · « **Reply #1 on:** May 28, 2006, 01:49:46 PM »

Helicoil, The old thread is reamed out and a hard "spring" thread insert in put in, If it's no 2 you may have to remove the head. I Had a mate with a kwak (Z650) he had a pot helicoiled and they did in situ (Cool)

KB02 · « **Reply #2 on:** May 28, 2006, 02:23:47 PM »

yeah, Heli coil sound like your best bet. Check your compression, though on all four cynlders to see if that one too high or if they are all right in line (within reason, of course...)

bguerr · « **Reply #3 on:** May 28, 2006, 03:47:53 PM »

has someone stripped it out previously or did the head just fatigue and give out?
crap...never EVER would have expected that could happen...makes sense though,
....great now i'm gonna be watching for that too
My luck i would be sitting behind a cop and the plug would fly our sound like a gunshot, break his window and i'd be getting my ass shot

Tim. · « **Reply #4 on:** May 28, 2006, 04:54:22 PM »

How are the rest of the plugs? I'd be concerned that if the previous owner or whoever blew it on #2, the rest are ticking time bombs (literally).

Andrew Foss · « **Reply #5 on:** May 28, 2006, 09:08:11 PM »

i have pulled #1 and #4 a few times (if you've kept up with any of my posts then you might know i have had trouble with cyl #4 not firing all the time) but had never touched the inside ones. this was 100% an unforseen problem, but considering the previous owner (if i could list all the bull.... i would, many things done WRONG when i got the bike) i should not be too surprised. to get it to ride for now i'm gonna thread it in with aluminum foil around it until my shop can get it in there to pull the motor (i'm asuming they will have to) and fix it for real. you would be surprised how well the aluminum foil thing has worked in the past (particularly with stripped allen heads) so i figure i'll give it a shot and see if i can't ride around while like that.
-andrew
PS- "many things done WRONG when i got the bike...i'm gonna thread it in with aluminum foil around it" (i see the contradiction....)

scondon · « **Reply #6 on:** May 28, 2006, 09:34:24 PM »

Aside from possibly pushing aluminum thread shavings into your combustion chamber, I would think that heat and compression would just blow the "aluminum foil" fix out again. Your bike, your call.

Andrew Foss · « **Reply #7 on:** May 28, 2006, 10:54:50 PM »

ahhh...good point, i'm gonna give it a whirl still. the bike is a rat, and i just want to ride it. i will get it fixed properlysoon. i mean, i rode it home with the plug just hangin' there, so if i have to again, i will..
-andrew
ps-it happenned around 23rd and Erie for anyone who lives in philly...had to get outta there.

DammitDan · « **Reply #8 on:** May 28, 2006, 11:05:27 PM »

The bike may be a rat, but you'll save yourself a headache later by not riding it on only 3 cylinders now.

I speak from experience that impatience to get back on the road just screws you over bigtime in the end (I've had to rebuild my top end 6 times now... and I'm going for a 7th soon...)

Unless of course you're a masochist... In that case, ride like the wind brother!

mrbreeze · « **Reply #9 on:** May 29, 2006, 12:27:41 AM »

W in TF am I reading here? This is definely one of the craziest posts I think I have ever read!!!!!!(I think I'll build a motor out of rubber!!!!!!!)

mrbreeze · « **Reply #10 on:** May 29, 2006, 12:46:22 AM »

I would have named this post AWWWW #$%*!!!!!!!!!!.......instead of.........oh dear!

puppytrax · « **Reply #11 on:** May 29, 2006, 05:00:23 AM »

Quote from: Andrew Foss on May 28, 2006, 10:54:50 PM

ps-it happenned around 23rd and Erie for anyone who lives in philly...had to get outta there.

I owned an Austin-Healey 100-6 while at the Philly Naval Hospital in '71...Took a friend back into Philly a year later to pick up some stuff...We were in that general neighborhood early on a sat morn...my friend saw a car up on cinder blocks; said "Someone's working on their car early"...I started laughing...after about the third car on blocks, he said "Oh Sh*t!...Let's get outta here!!!"...

Tim. · « **Reply #12 on:** May 29, 2006, 06:30:27 AM »

I say lose a carb, cut the wire and call it a triple. Then, you can later call it a twin, then a thumper, and eventually an anchor

puppytrax · « **Reply #13 on:** May 29, 2006, 06:39:06 AM »

Might as well loosen/remove the rocker arms on that cylinder, too...save gas...

smashme33 · « **Reply #14 on:** May 29, 2006, 07:47:36 AM »

heh, might as well pull the piston and con rod outta there too!

DammitDan · « **Reply #15 on:** May 29, 2006, 10:37:36 AM »

And overbore #3 to 836 to compensate for the loss of #2.

Andrew Foss · « **Reply #16 on:** May 29, 2006, 12:32:33 PM »

hey all. well here's an update. after looking very closely, there are NO threads at all in the head, which squashes the foil thing, not that i really expected it to work, but hey it would have been nice to ride to the shop on 4 cyl. well, i am going to call liberty cycles tommorrow (the owner hates my bike already...so i'm sure he will get a kick out of this one).
the owner told me i should have taken my old carbs (from the wrong year bike) carb holders (heated to make the wrong carbs fit, and the sealed with plummers putty) wiring harness (completely effed up) and gone to his (previous owner) house and beat him to death with the parts.
anyway, he will probably have an old 750 top end sitting around and just replace it rather than the helicoil (in which case, i will do the work myself), either way, im not looking forward to taking the subway to school while it is off the road in this awesome weather.
this bike has taught me one very important lesson, which is to inspect a bike vey carefully before buying, because with the money i have invested in this, i could have had a much nicer 750. but i'm not giving up on this one yet.
-andrew

bguerr · « **Reply #17 on:** May 29, 2006, 07:15:34 PM »

Quote from: Andrew Foss on May 29, 2006, 12:32:33 PM

this bike has taught me one very important lesson, which is to inspect a bike vey carefully before buying, because with the money i have invested in this, i could have had a much nicer 750. but i'm not giving up on this one yet.
-andrew

something i am learning too...
the hard way
good luck

theunrulychef · « **Reply #18 on:** May 30, 2006, 05:20:18 AM »

23rd & Erie - ouch. I've been temporarily stranded in some unsavory places as well. Good thing people generally don't want to f*$% with the biker who's got a beater ratbike. Once I was broken down at 26th & Diamond with flames shooting out of my tailpipe. Nobody came within 20 feet of me.

-Jay in Philly

kevito · « **Reply #19 on:** May 31, 2006, 11:57:05 PM »

I've seen what you have experienced first hand. It seems that some of the Honda cast engines were constructed (only a few of them) out of a strange alloy mix which is extremely sensitive to something in the oil or something in the air. My old CB350F1 engine was one of those motors.

The aluminium actually looks a dark grey, not a bright shiny grey. The metal is soft to the touch and is easily scraped and scuffed. The other CB350 motors I have are not soft like that. The air cooling fins are easily broken off. I also managed to crack the oil pan using only a small hand wrench (very light force, if any at all) when screwing in the drain bolt. The cam tensioner bolt sheered off as if it was made of plastic (again, light force). I also removed the threading from the spark plugs while tightening them 'finger tight' and the exhaust flange bolts also came clean out (threads and all) under 'finger tightening'.

I had to get a new engine. Things just kept breaking off under little or no force. There was a lot of metal garbage in the oil pan every time I changed the oil, and it got progressively worse. I don't know what the hell is wrong with the block as the internal parts are fine. The block itself was deteriorating inside and out. I don't know what could have caused it. It had 67,000 miles... but that’s not an excuse for metallurgical problems...

Andrew Foss · « **Reply #20 on:** June 01, 2006, 08:01:00 PM »

since the event, i have been told that it is a common problem among people who race the bikes and are putting sparkplugs in and out often. i was told that many racers will take a perfectly good head and put in helicoils or timeserts because they are more durable and reliable than the aluminum head itself. i have the motor out and am getting it fixed either tomorrow or saturday (need a ride to the shop) and i am going to have him drill out both inside plug holes to be safe.
on the plus side, i had a chance to clean my bike and replace all of those crappy phillips head fasteners with an allen set, and to repaint my engine (i havent done it all, but it is getting done before i reassemble)
i also just got my k fender (time to get out the sawzall) and i have a temporary seat to fit up. should be a much nicer (looking) bike when i get back on the road.....will post updates.
-andrew

Sam Green Racing · « **Reply #21 on:** June 01, 2006, 10:54:08 PM »

If it was me, I would put the plug back in, put the plug cap on, then wedge a big piece of wood between it and the frame/tank.
It should keep it in and as you said, it's only a rat bike so dosen't matter what it looks like.

Sam.

BTAYBA.

Terry in Australia · « **Reply #22 on:** June 01, 2006, 10:55:55 PM »

If the engine's out of the frame you should be able to helicoil the plug hole without removing the head, I've done it myself and it's not hard. Make sure you use plenty of grease on the tap so no more particles fall in the cylinder, and a little "Loctite" on the helicoil will keep it from winding out again when you remove the plug next time.

Most times a plug strips out a thread on an old SOHC4 it's because either it was cross-threaded last time, or the previous owner never did a plug change and the old plug has welded itself in due to "Electrolysis", (not the way Raul keeps his chest hair-free) a chemical reaction between by steel and aluminum. Make sure you use a little "anti-sieze" compound when you re-insert your plugs, and you'll be fine. Cheers, Terry.

Terry in Australia · « **Reply #23 on:** June 01, 2006, 10:57:29 PM »

Quote from: samcr750 on June 01, 2006, 10:54:08 PM

If it was me, I would put the plug back in, put the plug cap on, then wedge a big piece of wood between it and the frame/tank.
It should keep it in and as you said, it's only a rat bike so dosen't matter what it looks like.
Sam.
BTAYBA.

Hey Sammy, you weren't the general manager of Norton/BSA/Triumph back in the 1970's were you?

Sam Green Racing · « **Reply #24 on:** June 01, 2006, 11:11:49 PM »

Quote from: Terry in Australia on June 01, 2006, 10:57:29 PM

Quote from: samcr750 on June 01, 2006, 10:54:08 PM
If it was me, I would put the plug back in, put the plug cap on, then wedge a big piece of wood between it and the frame/tank.
It should keep it in and as you said, it's only a rat bike so dosen't matter what it looks like.
Sam.
BTAYBA.

Hey Sammy, you weren't the general manager of Norton/BSA/Triumph back in the 1970's were you?

Tell, you didn't ask what BTAYBA means

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Author Topic: ohh dear...spark plug shoots out of cyl #2....do i need a new engine??? (Read 6326 times)

Andrew Foss

bguerr

Andrew Foss

Andrew Foss

smashme33

Andrew Foss

bguerr

theunrulychef

kevito

Andrew Foss