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Discussion Starter #1
So I took my bike in for its first service since buying it, and was informed that the previous service cross-threaded the rear cylinder spark plug. They were able to get the new plug to torque to spec, and applied a bit of LocTite to make sure it held (the temporary stuff, not the chemical weld stuff). Has anyone had success using a heli-coil thread repair kit in this kind of application, or am I just going to have to replace the head? Seems that given the soft material heads are made from, this isn't that uncommon of a problem and there has to be a solution that doesn't involve a new head.
 

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Short answer is yes, heli-coil is exactly what you need for a stripped spark plug hole.

A previous owner must have been tightening the plugs without a torque wrench - its very easy to mess up the threads in alum in you dont use a torque wrench, and then the next time its easy to cross thread it.
 

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Discussion Starter #3
Thanks - my only concern was I was told there wasn't enough material to drill out the bigger hole required. I'm wondering if he was just trying to upsell a head replacement.

Yeah, I have learned the hard way myself that tight is tight, and too tight is broke. On the bright side, bike is running fine for now. Hate to have it in the shop this time of year!
 

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If Lesblank does not pick up on this when its morning in Houston, maybe send him a PM and ask for his input.

Im not sure if the threadlock will keep the plug in place. I would not take any road trips till you find out for sure. There is an incredible amount of pressure in the cylinder when the mixture burns, I have heard of people having spark plugs blow out of their heads in cars (because they were stripped out).

To fix it the hole is normally drilled out larger and tapped, and this is exactly what they are for, so unless someone really got in there and buggered it up a heli-coil should fix it properly.
 

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Discussion Starter #5
Thanks for the info. Yeah, I don't think having a rear cylinder plug blow out into my crotch would make for a very pleasant ride.
 

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Good morning, a little busy at work and just jump on site at break. My first try would be thread chaser. With any luck there are enough threads to clean. Make sure and put some grease in side grooves to catch metal shavings from going into cylinder. Lots of utube videos out there.



Second option would be a make a thread kit. I've used these on aluminum race heads and work pretty good.



Last option would be heli coil. The heli coil is actually the best solution but more labor intensive. They make thin wall heli coil so should be plenty of material to drill insert. Good luck and keep us informed.
 

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Discussion Starter #7
Thanks for the info lesbank. I'll let you guys know what I end up doing. Guess if I ever buy another used bike, I'll remove the damn spark plugs to make sure the previous owner didn't bugger them up!
 

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It can be hard to tell - its best to talk to the previous owner, ask him who did the maintenance on the bike, what kind of experience and tools he had

when I got Ursa it was running rough. When I decided to change the plugs I discovered they were only finger tight, which did no harm, but yeah... yikes!

Finding a used bike with low miles that is completely stock is gold - the less a person did to the bike, the less chances for them to mess things up.
 

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Discussion Starter #11
I have successfully used them before. Good product.
Is it as straight-forward as the instructions make it look? Looks to be as simple as tap new threads, cut seat, install insert. Did you use their sealant, or did you install it dry?

Thanks again.
 

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I used their sealant. Important to go slow and presise on the installation. Make sure and watch several videos and get comfortable with the process. It's not hard but really only have one chance to get it right. I really would try using a thread chaser first. If there are enough threads to keep the plug in, it might clean them enough to fix it.
 

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Discussion Starter #13
Well, cleaning up the threads didn't work. Time to order a time sert. Also, word of advise...make damn sure the tap is tight in the handle chuck. Fishing it out of the cylinder with a magnet is not fun. Dumb luck is the only thing keeping my bike off a trailer to have the engine pulled.
 

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I cross threaded a plug hole last year. I was able to get a plug in and torque it. I've been getting surges ever since. (Not certain that's when it started). I wonder if it's not seated properly and that's what's causing the bucking. The surges are infrequent though.
 

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^set screws suck
Yeah, the sound of the tap hitting the piston made me sick to my stomach. First attempt to retrieve it with a magnet resulted in the tap being perpendicular to the hole - not good. I must have fished around in there for 20 minutes and finally pulled it up through the hole.

I cross threaded a plug hole last year. I was able to get a plug in and torque it. I've been getting surges ever since. (Not certain that's when it started). I wonder if it's not seated properly and that's what's causing the bucking. The surges are infrequent though.
Mine was in the same boat - got it torqued (added a little loc tite for good measure), but after about 100 miles on it, it started running pretty rough. Everything else on the bike was fine, so I figured that had to be the problem. When I took it out to chase the threads, it was definitely working itself loose. Thread chasing didn't fix the problem, so next weekend I'm putting in a time sert. Based on how far Yamaha put the plug down in a hole, I'm going for the extended version. It's an extra $75, but I'd rather have an extra few inches and not need them than get the kit and not be able to get tools in the right spot. I'll try and post some pics of the process when I do it next week.
 

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Discussion Starter #17
So I completed the time sert installation this weekend, and so far so good. The kit is very straight forward to use. I did buy the extended repair kit, due to how far down into the head the plug is, and I'm glad I did. It would have been very close to being too short (amazing what a couple extra inches do), so well worth the extra $80. A couple of notes for anyone else that might need to do this:
1. I used heavy red grease in the flutes of the tap to catch shavings. It worked great.
2. I used too much heavy grease (and a little too much thread sealant on the insert) and had to clean it off of the plug mounting surface. Being way down in the cylinder head, this was not fun. My fingers weren't long enough to reach, so I ended up putting a rag over a large Philips head screwdriver to clean the surfaces.
3. Make sure you take the treads deep enough, else the countersinking tool hits the tap and doesn't allow for a good surface.
4. Using a small hose on a shop vac allows you to vacuum out the cylinder, just in case some shavings drop off the tap. I actually had a guy at the bike shop recommend I do it dry to the shavings vacuumed up easier, but the time sert instructions specifically say to use grease, so I did. Based on the shavings stuck to the tap when I was done, the grease captured pretty much everything (confirmed when I didn't suck much out of the cylinder afterwards).

Overall, it took me about 45 minutes from the time I took the cover off the bike until I put it back on. I let it sit overnight (allow the thread sealant to cure on the insert), put the plug back in Sunday and it fired right up. Total cost was about $260 for insert set and sealant and about an hour of my time. Much better than the $1200 the dealership wanted for a new head. I'll update more after I put some more miles on it. I'm kind of limiting myself to short trips for a bit just to make sure everything is as it should be.
 

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Nice work! Its very satisfying to be able to fix something that had rendered the motorcycle un-usable.

I hope you dont mind for future reference and people who will find this thread looking for solutions. Your experience is valuable relating to 2 things:

1. If you are able, its better to do the most basic maintenance on your motorcycle (and car) yourself. You have the most interest in getting it done correctly, and if you feel you are getting in over your head you can always stop, ask for help, or have someone else do it. The easiest way to mess up an engine is to make a mistake changing the oil, or things like changing the spark plugs. If an engine is run without proper oil levels and oil weight it can be ruined in a matter of minutes on the road. Same with things like torquing a spark plug into the aluminum head - its really hard to have the plug so far off center in that nice round port that it will cross thread. The damage is usually caused by someone tightening the plug by hand. The feel of a steel plug or drain bolt into steel is very different from the feel of steel threads into aluminum (heads or engine case).

No one cares about your bike more than you, no one is standing there saying "you have to be done in 20 minutes, there are 8 more bikes to get finished by 5PM". You can take your time, double check everything, and do it perfectly.

2. Already explained the problem about steel threads into aluminum. Everyone that wrenches on a motorcycle should get a torque wrench before they buy any other tools. Stripping out the spark plugs or the drain plugs is a very common mistake, and its expensive to repair (even if you fix it yourself). Use a torque wrench on your plugs, the oil filter cover plates, the axles when you pull your wheels off - any bolt that is going into aluminum WILL last forever if it is correctly torqued, over and over, it will not strip out if its torqued correctly.

A 3/8" torque wrench that goes up to about 80 ft-lbs should be all you need for every bolt and fastener on your motorcycle, unless you start tearing into the engine (clutch plate or flywheel bolts... maybe).

The Yamaha factory service manuals for pretty much all V star bikes have been scanned and posted on the internet in PDF format and can be found as free downloads. All the torque specs are in the service manual, a few of them are in the owners manual, which can also be download free (directly from yamaha website).

Motorcycles are very simple machines and most maintenance is easy to perform, the manuals are out there, the tools are not expensive. Personally I cannot imagine paying someone else to have the pleasure of working on such a well designed and manufactured machine.

The flip side of this, if you dont feel you have the ability to wrench on your machine, you need to find a good mechanic you cant trust as if your life depends on it, and recognize a good mechanic is worth his salary.
 

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aryj2004, very good work. Glad it worked for you. Definitely post after a few good rides any issues you notice. I would recommend to recheck plug torque after a few rides.
 

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Nice work! Its very satisfying to be able to fix something that had rendered the motorcycle un-usable.

I hope you dont mind for future reference and people who will find this thread looking for solutions. Your experience is valuable relating to 2 things:

1. If you are able, its better to do the most basic maintenance on your motorcycle (and car) yourself. You have the most interest in getting it done correctly, and if you feel you are getting in over your head you can always stop, ask for help, or have someone else do it. The easiest way to mess up an engine is to make a mistake changing the oil, or things like changing the spark plugs. If an engine is run without proper oil levels and oil weight it can be ruined in a matter of minutes on the road. Same with things like torquing a spark plug into the aluminum head - its really hard to have the plug so far off center in that nice round port that it will cross thread. The damage is usually caused by someone tightening the plug by hand. The feel of a steel plug or drain bolt into steel is very different from the feel of steel threads into aluminum (heads or engine case).

No one cares about your bike more than you, no one is standing there saying "you have to be done in 20 minutes, there are 8 more bikes to get finished by 5PM". You can take your time, double check everything, and do it perfectly.

2. Already explained the problem about steel threads into aluminum. Everyone that wrenches on a motorcycle should get a torque wrench before they buy any other tools. Stripping out the spark plugs or the drain plugs is a very common mistake, and its expensive to repair (even if you fix it yourself). Use a torque wrench on your plugs, the oil filter cover plates, the axles when you pull your wheels off - any bolt that is going into aluminum WILL last forever if it is correctly torqued, over and over, it will not strip out if its torqued correctly.

A 3/8" torque wrench that goes up to about 80 ft-lbs should be all you need for every bolt and fastener on your motorcycle, unless you start tearing into the engine (clutch plate or flywheel bolts... maybe).

The Yamaha factory service manuals for pretty much all V star bikes have been scanned and posted on the internet in PDF format and can be found as free downloads. All the torque specs are in the service manual, a few of them are in the owners manual, which can also be download free (directly from yamaha website).

Motorcycles are very simple machines and most maintenance is easy to perform, the manuals are out there, the tools are not expensive. Personally I cannot imagine paying someone else to have the pleasure of working on such a well designed and manufactured machine.

The flip side of this, if you dont feel you have the ability to wrench on your machine, you need to find a good mechanic you cant trust as if your life depends on it, and recognize a good mechanic is worth his salary.
I don't mind at all. The part that really gets me the most on this is I am fully capable of doing the maintenance, it was just easier to take it elsewhere. That is, until elsewhere messed it up (I have no way of knowing if previous owner over torqued it or if my mechanic here did). Besides, my 10-year old is showing some interest. Hopefully I can make some mechanic memories with him like I did with my old man when I was in high school and couldn't afford to take the car to the shop.

Adding to your point about a torque wrench, I threaded the plug by hand until I felt it bite, then put the torque wrench on it. Plug torque is 9.4 ft-lbs for the spark plugs on this bike, and I will say that just under 10 ft-lbs does not feel like the thing is tight at all. No way I stop myself from over-torquing without a proper torque wrench.

While I did manage to get out of the cost of a new head, in hindsight, I'd rather have spent the $260 on a bike lift and some tools, or maybe even something fun than fixing stupid. Lesson learned, and unless it involves removing and/or tearing down the engine, I'll likely be turning my own wrenches from here on out.

Thanks again to all that provided guidance.

aryj2004, very good work. Glad it worked for you. Definitely post after a few good rides any issues you notice. I would recommend to recheck plug torque after a few rides.
Yeah, I'm definitely going to be checking on plug torque over the next few weeks. I figure if I get 500 miles or so on it with no issues I should be in good shape. More to follow!
 
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