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85 XJ700N broken Bolt, can't find bolt size.

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So I have an 85 Maxim XJ700N. bought it a couple weeks ago. Due to it sitting for over a year I was doing some check up on it. Did compression and spark test and pulled the carbs to check for corrosion in the bowls. Well I couldn't get the carbs back on. so I figured I would take cyl 1 and 4 Intake boots off and put them on the carbs myself so I'm only pushing onto the middle 2 boots. well one of the bolts for the cyl 4 intake boot broke. I tried using a welder to get a nut on the end and losen it but it would not budge and the nuts would just come off. I suspect I'm just still not good at welding. so I turned to extractors. after getting a little into the bolt with a Titanium HSS bit we were trying to back the screw out with the extractor when the tip broke off. SO I'm done with it. I have a 7/32" Colbalt Drill bit and I'm going to drill it out completely. I also want to order an EZ-Locke insert but I don't know the bolt thread. I thought it was M6 x1.25, but the 7/32" bit I bought at Home Depot is slightly smaller than M6 bolts. well when I got home and checked it against the bolt I have it's about the same size as the bolt(including the threads) I suspect this to be M4x1.25. but I wanted t o make sure. I have a PDF of the Service manual but the bolts are not listed anywhere. I checked a Yamaha parts dealer I used for my Zuma I had a few years ago, but they don't have the size of the bolts just a price. I live outside of Town, have limited transportation and forgot to take the bolt with me when I went to home Depot earlier.

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Hi Ratch,  don't worry we've all snapped off intake/exhausts studs at some point in our biking!!

All yamaha bolts/studs are all going to be metric. It won't be M4 as thats only 4mm across and nearer to 9/64 drill bit. its going to be M6 (6mm across) All studs are.

There's a good lot of metric/imperial conversion charts out there, but finding the exact info you need is not always easy.

As we're not allowed to put in links to copyright material just google "screw sizes and drill equivalent" and you'll find a 7/32 drill is equivalent to an M6 screw size. A website pdf with 'little machine shop' in its title has a nice chart.

As regards to the stud itself, there is a very good parts catalogue website called cmsnl. You may have already found it.  Just look up your own motorbike and you'll be able to find the appropriate exploded diagram of ALL the parts, including the part number to the bit you are looking for. Armed with the correct part number, google and ebay ebay will give you access to them. Be careful on exhaust studs, often the part which screws into the engine is a courser thread than the nut which screws on the end. 

Hope this has been helpful to you.


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the good news, got the bolt out today. Cleaned it up and double checked the threads by carefully screwing in one of the other bolts. had no hitches. so a replacement bolt, and gaskets and the carbs will go on and not come off for a while.

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