Stripped Spark Plug

[Represto]

My first post on this board will be one of equal parts excitement and mind numbing frustration.

First off, I just got my 1978 CB550K on the road. I bought it off a fellow who floats around on this message board and I love it. I took it to the shop after the purchase to get it road worthy and safetied. $600 later all is almost good.

The 2nd spark plug is stripped. It's not flying out or anything but it's running rough. I figure these are my options...

Replace the head with something like this
The part is about $250 shipped + labour. Labour seems to be about $80/hour. I'm guessing 2-3 hours??

or

Rethread or helicoil. The (very) rough estimate on this was $1000. Does this not seem insanely high?


In the mean time, is there anything I can do to temporarily fix this? Can I not put some kind of sealant on it to at least help it to run a bit better?

Thanks.

 

[matt365]

I'd assume they would be dissassembling the whole motor to put in a coil for that kind of coin.

You could try and helicoil it yourself. The trouble I'd guess would be getting metal shavings inside the cylinder. You'd have to drill out the existing thread, and if the shavings are magnetic, get one of those magnetic extendable tools (looks like a collapseable antenna with a magnetic tip) to get all the shavings out. Either that, or get the cylinder dry enough that the shavings won't mix with oil and use a shop vac to suck out the shavings.

Then you could just tap it with the helicoil tap, and drop in a coil.

You could try and find a spare engine?

Or just try and use some high temp gasket sealant and hope it holds.

 

[Tim]

Pulling the head off the 550 is not a big deal - a few hours and the manual. You're in Toronto right?

What I'd be doing, depending on the condition of the bike / valves etc. is probably I'd find a good head (lots of 550 heads around), take it in for a valve job, and then swap out the heads.

$1000 for a Helicoil is nuts. A 550 head should cost you about $50 tops. Valve job would be $200 or so. Only parts you'd need are new stem seals and a head gasket.

Of course you can opt to skip the valve job, and just spend the $50 on a head and another $40 or so on a head gasket. Someone who knows what they're doing could likely swap the heads out in 3 hours tops. It's dead easy.

Start looking for a new head - post in the wanted section of the board. I know there are lots of 550 heads around Toronto. I used to have a couple of them in my garage myself.

 

[Represto]

Pulling the head off does sound like a big deal for me...I'm not the most mechanically inclined and this is my first bike. I just got off the phone with a different shop and they said it would be a 4 hour job @ $55/hour + the coil ($40). This sounds more reasonable to me.

What is the going rate for bike mechanics? $80 is significantly more than $55...

 

[Tim]

$55 / hour is pretty good for shop labour. Try Cyclewerx and 109 Cycle. Which end of town are you in?

What exactly would they be doing in the 4 hours? Sounds like they'd be removing the head.

For the $40 cost of the helicoil, I'd seriously look for a different head and swap them out. Same labour - maybe less as no helicoil to do.

 

[Represto]

I was talking to The Motorcyclist. I'm downtown (College/Bathurst), so I think this is the closest shop to me. He said that they'd take the head out to avoid issues with the shavings. It'd rather pay a bit extra for them to take it off the bike than to risk it.

I'm going to shop around for a head to see if I can find something good.

 

[clt750]

I stripped the #4 on my CB350F. That's is a good way to ruin your night. I tried the Helicoil route myself. The only thing I got out of it was that I am no machinist. I replaced the whole head. $50.00 in town used. I am not sure on the 550's head but the 350F's are simple. I guess if the Helicoil is done right it would work. After I drilled it out I realized that I came very, very, very close to the edge of the valves. I was just not sure that this was a good application for the Helicoil. So I replaced the head. Obviously I was unsure if it would work, and I didn't want to turn around and have to take the head off again.

 

[Represto]

How was it to replace the head? Did you have to drop out the engine?

 

[clt750]

Not on the 350F. The valve cover comes off, then the head. Motor stayed in place. It is one of those jobs that will take some time the first time around. The second time will be a snap.