Tapping downpipe bolts

[Raf]

Ok so a few weeks ago whilst servicing my cbr 600 fm i was changing the oil and managed to lose the crush washer. Instead of walking to a motorcycle shop, buying a new one and doing the job properly like i should have i thought hell to the crush washer and went on without it. Long story short i stupidly managed to crack the oil sump by over tightening the sump bolt.

Anyway so i managed to bodge up the crack with some liquid metal and strong poxy. But it leaks when the engine heats up so needs to be replaced.

My first problem is that i can't find an oil sump/pan for the bike, not the exact year anyway. Does anyone know if other models might work? The shape of the gasket seems the same on almost all them, but the overall designs are slightly different.

Second problem. The downpipe bolts are seized on, one has already broken off. I have tried heating them and using penetrating fluid. I know a few of them will give but i also know one or two that will brake off no matter what.

What size drill bit do i need and what kit should i be using if i want to retap the downpipe bolts?


Many Thanks
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CBR1100xx - BMW K1100 - BMW K100 - Triumph Sprint ST 955i - Suzuki GSX-R 600 - Suzuki DR 350 - Yamaha XV 750 - Honda CBR 600 FM - Yamaha XT 600 - Yamaha Rs 200 - Honda NSR 125

[bladerunner]

if they are M6 (10mm bolt head and usual honda size) then you want a 5mm drill in aly. it's not a hard job if you can get good access but if your doing it engine in situ and frame etc in the way you'd better be pretty savy with a pistol drill!!! Usual things are to get the snapped off stud head as flat as possible and ideally flush with the surrounding casing. Make sure you center punch it smack bang in the middle and measure the depth of the threaded part from one that has come out ok. I've seen someone drill right through to the water jacket because of not doing this before!!!

I usually use a machine tap (spiral flute) as they dont need turning back half a turn every 2 turns and I use a cordless drill with the clutch set to disengage when the tap bottoms out.

If you wander off center with the drill then you'r going to have fun as the ally is a lot softer than the stud steel and the drill will stard to cut sideways!!!! Not ideal! and whatever you do dont snap the tap off in the hole either..hard as buggery them and you end up having to grind them out......it's at this point I usually get asked to give a "hand"


if you don't manage to get a clean tapped thread into the original hole then have a look at getting a recoil or helli coil kit. this involves drilling a 1/4 or 6.3mm hole and tapping it out with the tap in the kit and then screwing in a hard wire thread that once done will not give you the same problems again!!!!

last option is to drill out with a 6.8mm drill if you retap the hole to M8..but you might have to open out your exhaust clamps to take the 8mm studs a little!!

good luck!!
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[stinkwheel]

Making a drill guide out of a block of alloy on a pillar drill that bolts to the studs either side of the snapped one will help keep things on centre if you're drilling exhaust studs with a pistol drill.

Consider using a hand drill, it's slow but you get a lot more control.

When you re-fit the new ones, use brass nuts to hold the headers on. These should be very resistant to seizing and their threads ought to strip out before the stud snaps if they do seize.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Raf]

Thanks for the help. Im going to give it a shot this weekend and see how it goes. Im expecting the worse. But im ready to have a crack at it. Worse come to worse i will just bite the bullet and buy a new engine.
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CBR1100xx - BMW K1100 - BMW K100 - Triumph Sprint ST 955i - Suzuki GSX-R 600 - Suzuki DR 350 - Yamaha XV 750 - Honda CBR 600 FM - Yamaha XT 600 - Yamaha Rs 200 - Honda NSR 125