I screwed up torquing bolt - Please help

18 replies to this topic
  • Stumped

Posted October 18, 2004 - 12:39 PM


:cry: OK, I screwed up BIG time. I did the cam mod with Hot Cams, everything went great (well almost), I torqued the freaking bolts to spec and actually set it a little lower and the last freaking bolt sheared off.

Also, I am not sure that I rotated the cam one sprocket back.
I am not a mechanic, at least not a good one...
What is my best solution? Should I take it to my local shop or try to drill it out myself (I don't have the tools to do that anyway)?

  • tc66nova

Posted October 18, 2004 - 01:27 PM


Do you know a COMPETENT machinist? I fix that sort of thing all the time. But if you are not qualified and or don't have the right equipment DO NOT touch it. I have fixed alot of broken bolts that took a couple of hours that the owner had tried himself. With the right tools it usually takes just a few minutes. The right way to do it is a center drill to locate and then try a left hand drill. Usually the drill will catch as it goes thru and run the bolt right out.

  • jespertheil

Posted October 18, 2004 - 01:38 PM


Exactly like tc66nova said... DON`T try to fix what is broken....
Take it somewhere with the right tools..
If you try to drill it out, you might end up with a lot of metal falling further down resulting a casesplit also... For a pro this problem can be over in 30 minutes or less..

  • YZ250F_Rider

Posted October 18, 2004 - 01:49 PM


The cost to get it fixed will be a lot cheaper than to replace the head if you butcher the repair. Let somebody help.

  • tc66nova

Posted October 18, 2004 - 02:32 PM


Stumped, where do you live? If you are anywhere near Ohio I would be willing to help you out.

  • Stumped

Posted October 18, 2004 - 04:31 PM


Hey thanks for the offer, but I'm in Maryland. I'll take it to my local shop.

freakin yamaha manual.

  • SXP

Posted October 18, 2004 - 04:40 PM


freakin yamaha manual.

There is nothing wrong with the manual - thousands of us have used it with great success :cry:

Are you sure you were torquing the cam cap bolts to inch-pounds and not foot-pounds?

  • Stumped

Posted October 18, 2004 - 04:42 PM


Uh, I was doing foot pounds as it stated 7.2 ft/pds.

  • SXP

Posted October 18, 2004 - 04:49 PM


What's the range of the foot-pound torque wrench you are using?

For something that low, I'd use an inch-pound torque wrench (86.4 inch-pounds)

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  • sirthumpalot

Posted October 18, 2004 - 05:06 PM


Are you using a clicker wrench, or one of those that bend? Use a good clicker wrench. Don't get one of those $10 jobs, go ahead and drop some cash on a good one and have it calibrated often.

In regards to the head; will the caps come off if you remove the rest of the bolts? If so, is there enough bolt sticking out that you can unscrew it with your fingers? Otherwise personally I would take it to someone who has done that before. Not a big deal with the right tools.

Also double check the torque. I always use Nm and not ft/lb so I'm not sure how tight 7 ft/lb is but it sounds high. Going completely from memory (which isn't very good lately) I think the torque for the cam caps is something like 10Nm, which is not very tight at all. Someone with the manual please double check me on this.

  • cowboyona426

Posted October 18, 2004 - 08:18 PM


A quick way to check if your torque spec is too high is to try and turn the cams by hand- they should be able to be easily rotated by hand. Also, see my post in the YZ 450 cam mod thread. I would definitely not try what I suggested if you are at all unsure of your abilities though.

  • Stumped

Posted October 19, 2004 - 05:33 AM


I was using a clicker wrench, no it wasn't cheap.

I followed the manual. I did it in a cross pattern, yet the bolt still sheared.

Not really interested in the CSI for why it happened, but thanks for the input to fix the problem :cry:


Posted October 19, 2004 - 05:54 AM


Not really interested in the CSI for why it happened

No need to get so damn defensive... These folks are just trying to educate you. You ask a question you get an answer... That's what TT is all about.

Bonzai :cry:

  • Stumped

Posted October 19, 2004 - 06:07 AM


Dude, I'm not defensive, I asked the question - How do I FIX the problem...

I gave up caffeine 2 weeks ago so I am a little edgy, I'll give you that!

Oh, and I do appreciate the help, TT is great!

  • wrooster

Posted October 20, 2004 - 11:16 AM


How do I FIX the problem...

best accessory for working on yamaha's of all sizes:

available at sears for US$20 or so. left hand drill at one end, fine pitch extractor at other. works 100% every time, unlike those crappy coarse spiral fluted extractors. this kit has paid for itself 50x over now.

jim aka the wrooster
'01 wr250f

  • twistngrip

Posted October 20, 2004 - 03:35 PM


What happened to Stumped is probably the same thing that happened to me with my oil filter cover. Sometimes you can use the specified torque values and do everything right and for whatever reason they will twist off like they are made of butter. Stumped probably did everything right. I personally believe replacing bolts often is cheap insurance, especially on bolts that are going to give you ulcers if they twist off.

  • 426_Texan

Posted October 20, 2004 - 08:46 PM


Damned cheap Jap bolts :cry: :cry: :cry:

I break a bolt almost everytime I work on mine :cry:

  • yoshy

Posted October 21, 2004 - 02:14 AM


steel and aluminium is a very bad combination, i clean and lube every bolt i work on. makes wrenching much more fun :cry:


Posted October 21, 2004 - 04:43 AM


Torque Wrench... Torque Wrench...Torque Wrench.....

In addition, any bolt that is exposed to constant heating and cooling should always be inspected for strech marks and cracks before being reinstalled. Any signs of stress and the bolt should always be replaced. It doesn't take much to weaken these bolts and when they snap it can be very expensive to have repaired. I have invested in a metric time cert kit as well as a good bolt replacement kit both for under $60.00. It sure comes in handy an saves way more money down the road. Be careful when replacing bolts that go into the case with stronger ones though....You are asking for trouble when you do this, as you increase the chance of stripping or cracking the case when overtorqeing.

It may also be a good idea to purchase a (Left Handed Drill Bit Set) and an easy out kit. I have found many times that a very small left handed drill bit will extract a broken bolt on it's own if you take your time and use a variable speed drill. Just be carefull and watch your depth. I use a sharpie and mark the bit to ensure that doesn't happen.

Bonzai :cry:

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