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Post by Phil on Apr 17, 2023 17:53:38 GMT
Guys I'm after a bit of info please.
I need to know what size the and thread pitch the 250n head bolts are?
I know one of mine has stripped the thread from the block so I'm looking at a Helicoil set but obviously need the bolt size and thread pitch.
I heard somewhere that they were something like M10 with a 1.25 pitch but I cant help feeling the bolts are bigger than that.
grateful for any help.
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Post by marktrower on Apr 17, 2023 18:44:03 GMT
hello phil i will let you know tomorrow got a kit to do the same job some years back on a mates 250 but i think someone will give you the info before then
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Post by Phil on Apr 17, 2023 20:09:59 GMT
hello phil i will let you know tomorrow got a kit to do the same job some years back on a mates 250 but i think someone will give you the info before then Ok nice one thanks. I'll hold off pulling the trigger on the helicoil set just yet. |
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Post by buster on Apr 18, 2023 10:55:27 GMT
yep they're M10 1.25mm pitch, I'd forget all about helicoils, they simply arent up to the job for a cylinder stud, it needs a timesert repair
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Post by Phil on Apr 18, 2023 12:06:41 GMT
What makes you think they're not up to the job?
Ive used them over the years on all sorts of engines and fastners.
Touch wood up till now ive not had one fail.
Ive even double stacked the stainless steel inserts and used locktite.
From memory the head bolt torque is only about 24 lbs feet (not a lot really).
Having said all of that if someone has done it and had a failure im all ears as far as alternate ways of fixing it.
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Post by Phil on Apr 18, 2023 12:24:46 GMT
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Post by buster on Apr 18, 2023 12:51:01 GMT
I'v just scrapped a 250 upper crankcase for that exact reason, someone had done a helicoil repair, it may have seemed as if it was holding but it wasnt, all it did was screw up any chance of getting a timesert into it, not enough meat left on the aluminium to tap into, had it been done right in the first place it would have been a perfectly good casing. you also have to bear in mind the heat cycles it goes through as well as the torque
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Post by Phil on Apr 18, 2023 15:59:05 GMT
not heard of a "timesert", ill look into it thanks.
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Post by Phil on Apr 18, 2023 16:30:53 GMT
OMG time serts are hell expensive.
for the price of the M10 kit i can almost pick up a second hand engine.
I'm going to strip it down and see how it looks before deciding.
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Post by buster on Apr 18, 2023 18:05:01 GMT
OMG time serts are hell expensive. for the price of the M10 kit i can almost pick up a second hand engine. I'm going to strip it down and see how it looks before deciding. try a local motorbike shop, they'll most likely have the kit and charge you for one thread |
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Post by marktrower on Apr 18, 2023 18:43:03 GMT
timeserts vs helicoils one is a general purpose repair the other is more a specialist repair.both are stronger than the standard thread in alloy,i use helicoils a lot and even used the kits on ebay with good results the main problem with helicoils for applications like sump plugs and spark plugs where the item is removed a lot they do not do well .i get my kits from wti fasteners as they do more than metric not cheap but i do not do cheap but a lot less than timeserts.there is solid plug repair or filling with weld but they are strip downs and engineering work.over my working life and my hobby i have never had a helicoil fail and they are the size that buster said
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Post by Phil on Apr 20, 2023 12:25:46 GMT
timeserts vs helicoils one is a general purpose repair the other is more a specialist repair.both are stronger than the standard thread in alloy,i use helicoils a lot and even used the kits on ebay with good results the main problem with helicoils for applications like sump plugs and spark plugs where the item is removed a lot they do not do well .i get my kits from wti fasteners as they do more than metric not cheap but i do not do cheap but a lot less than timeserts.there is solid plug repair or filling with weld but they are strip downs and engineering work.over my working life and my hobby i have never had a helicoil fail and they are the size that buster said Thanks very much for the imput. To be honest you pretty much confirmed my thoughts. Ive never had a Helicoil fail either on and item that tighten up once a forgot it. If it was something like a sump plug being tightened and undone regularly id look at the alternatives. |
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Post by marktrower on Apr 20, 2023 18:51:45 GMT
its sods law you talk about something then it lands in your lap.a problem with a helicoil ,the coil did not fail the engine was running fine he started getting noisy on the top end he as had 8 years trouble free running .had problems getting one of the head bolts out so went through to give a hand .found this the helicoil had screwed out with the bolt .no1 they had not put the correct length coil in to long .no2 they should have used a screw lock coil they will not screw out .now if i can get the rest of the coil out without damaging the thread i will just fit a screw lock at the correct length as i cannot cut as the threads are 15mm down the hole if i fail i will fit a twin coil thats a helicoil that fits into a helicoil to get back to the correct bolt size.the main problems with helicoils is the people that fit them  |
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Post by Phil on Apr 23, 2023 15:49:29 GMT
lol that's typical isn't it.
to be on the safe side i do like do put a dib of thread locker on mine.
and if need be once its nice and dry run the correct tap (M10 1.25) gently down to check its clear.
(also blow the hole out with my airline).
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