Over Torqued head bolts =( please help ASAP

sergman89

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Jul 7, 2012
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I was out riding and of course 4 miles from my home I try to tighten my bolts since it sounded like it was loose, and felt it. You know like the power is weak, like before I first tighten them.

Then I over tightened the bolts, and snapped/stripped two of them. When I tighten no matter how much I ratchet, the bolts get a little tight then slip loose. I tried to run the motor with them as tight as possible but of course it shook loose, and gave 0 power. When I got home, I managed to get the bolts out all the way, and looked inside the holes best I could and couldnt see any broken stem. I could be wrong, I am not a vet at motors yet, still a journeymen/novice.

What are my options? Can I buy a slightly larger bolt and maybe it holds better?

I see people say to use a heli coil, and tapping the holes. I dont know what tapping really means, so if someone can briefly jist that up I would appreciate it.

What size heli coil kit should I get if I need it?

I appreciate the help guys, I feel like im going crazy with this thing. I swear my next build will be a perfect smooth ride, with all this F'ing up im doing atleast Ill know what not to do!.crt.
 

Kioshk

Active Member
Oct 21, 2012
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Yes, you must helicoil. Depending on engine, you'll need 6mm or 8mm. You can find these kits at automotive stores for like $30 (in the Northeast US at least). Instructions in the package. Good luck.
 

ajoh

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Mar 21, 2014
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https://www.youtube.com/watch?v=RFYa6sjhh_E

this will explain it for you re; helicoil an tapping.

as for what to do go to a local machine shop either with the bolt itself an get the matching helicoil kit to fix it yourself or
if possible remove the motor strip it down an take it to the machine shop with
all the bolts (head bolts) an they can do it for you it shouldn't cost much at all

reason i said take all the head bolts is so they can clean them all up for you (threads)
while doing the helicoil.

personally i'd get the machine shop to do it for you unless you are experienced with doing this kind of stuff.

good luck
 

mapbike

Active Member
Mar 14, 2010
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Central Texas
Look up installing heli coils on youtube and you can see the process, that is the simplest thing I can tell you right now.

If you engine is a china girl and has 8mm cylinder/ jug studs you will need to determine if you have 8Mx1.00 threads or 8Mx1.25 threaded studs, it seems that the latter is the most common but I have engines with both.

Or you can order a new set of studs with the other hardware from Sick Bike Parts at which ever thread you want and then buy heli coil thread repair kit to match the new studs, I would recommend the new studs personally.

Hope this helps ya a bit.

Map
.wee.
 

sergman89

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Jul 7, 2012
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The auto store doesnt have the M8 or M6 heli coil so I guess Ill have to go to a machine shop tomorrow. One is 5 mins from me.

How much should it cost for them to rethread this for me? And how can I take the other two head bolts off, the two that came off easy are because the threading. Because the other two are stuck on good.
 

sergman89

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Jul 7, 2012
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Thank you guys for these fast responses!!! I wish I still lived near the city, I had 5 auto stores near me. Now im in the woods, and apparently good for machining companies lol.
 
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2door

Moderator
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Sep 15, 2008
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The auto store doesnt have the M8 or M6 heli coil so I guess Ill have to go to a machine shop tomorrow. One is 5 mins from me.

How much should it cost for them to rethread this for me? And how can I take the other two head bolts off, the two that came off easy are because the threading. Because the other two are stuck on good.
Don't mess with trying to remove them. Just take the engine as is to the machine shop. They'll remove the other two studs if they feel it's necessary.

Price? It all depends on how hungry that machinist is. $25.00 sounds like a good starting point to me.
Good luck.

Tom
 

mapbike

Active Member
Mar 14, 2010
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Central Texas
You're welcome sergman89

Hope you have the little gal back on the road running good very soon

If they try to hit you with a big cost just keep in mind that you can buy an entire new lower for $60 -$70 + shipping.

Some machine shops charge around $75-$100 an hour.

Map
.wee.
 

sergman89

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Jul 7, 2012
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Ok so I went to Napa, and they had the Heli COil M8 x 125 I went to lowes and put this bolt I have through a M8 x 1.0 and it was a little tight to fit into the 1.25...

Can someone advise me on what to do.

I cant find a 1.25 bolt anywhere... BY THE WAY the machine shops charge to much, like 80 bucks is what they were trying to charge and giving me a hard time. So they probably didnt care for something this small scale
 

2door

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Staff member
Sep 15, 2008
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Littleton, Colorado
You can't thread a 1.25 into a 1 thread. They are course and fine thread and not compatible. You'll have to match the bolt/stud to the thread in the case.

If you have a 1.25 Heli-coil, you'll have to have a 1.25 stud to thread into it.

Apparently the machinist you talked to wasn't too hungry. They charge what they want if they don't need or want the business.

Tom
 

CTripps

Active Member
Aug 22, 2011
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...BY THE WAY the machine shops charge to much, like 80 bucks is what they were trying to charge and giving me a hard time. So they probably didnt care for something this small scale
Is that the only place you have around you to go to, or does he have some competition? It sounds like he couldn't be bothered unless it was a bigger job.

Crazy thought, but is there a high school with a shop teacher nearby? Someone like that could do it, possibly under the excuse of teaching a class how to do it.....
 

sergman89

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Jul 7, 2012
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****UPDATE*****

I got a 5/16 heli coil, and the drill bit for it cracked the drill hole wall going into the piston...

When I look at crank cases they are 35 bucks without any insides. Is there something that can tell me how to take apart this engine crank case correctly and put it into the other?
 

mapbike

Active Member
Mar 14, 2010
5,398
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Central Texas
****UPDATE*****

I got a 5/16 heli coil, and the drill bit for it cracked the drill hole wall going into the piston...

When I look at crank cases they are 35 bucks without any insides. Is there something that can tell me how to take apart this engine crank case correctly and put it into the other?
OUCH....!

best wishes buddy.... if you don't have an impact whrech the odds of you getting the internals out and sprockets and gears off are next to nun....

your best bet may be to just buy a new lower, put your cylinder and piston on it and start fresh, Thatsdax sells a very good lower assembly for 69.99 + shipping, there are others also but these lowers make for some really nice running engines in my opinion.

Map
.wee.
 

MEASURE TWICE

Well-Known Member
Jul 13, 2010
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Just so you know, 40 years ago in New York I had a motorcycle that I needed just one thread redone on a head. Back then just one re-thread with Heilicoil was costing $20. So actually it just seems unless you already have the whole setup for Heilicoil repair, the cost to buy just individual for one size repair still may mean you best look for some do-gooder at the high-school or replace rather than repair.

Where I am near San Jose, CA there are local places that specialize, but mail order can be done if you really want. The drills bit are special sizes and it is best to get the right bit for the job. A drill press also is handy.

Don't feel bad, I did actually try to drill out a rusted steel bolt on a aluminum cast block and veered into the crankcase.

Funny I can say now, I used a Heilicoil there to plug the veered off drill though and it holds to date. There is high temp red RTV on the threads keeping it sealed along with a split lock washer and a shaped metal block getting the right angle for it to hold. Instead now the fastener for the one of three bolts to hold the recoil flywheel cover I made with a bracket is going to one of the four engine hold down bolts. It is OK too.

Sometimes you can find ways of fixing things not normally done. See about the high school thing. It could be worth the try!

MT
 
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