Broken Crankcase 2002 Bonneville - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 94 (permalink) Old 02-29-2012, 08:33 PM Thread Starter
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Broken Crankcase 2002 Bonneville

The crankcase and crankcase cover broke on my 02 Bonneville where the starter gearshaft fits.

I plan to try a fix because I don't want to replace the crankcase, especially for the cost of a new one ($4000). I don't really want to spend the time and effort to replace the crankcase from a salvage bike.

I did see an ingenious fix on the forum where a drill bit was used to extend the length of the starter gearshaft and the crankcase was drilled out to hold the extended shaft. I may go this route.

I think the crankcase & cover is cast aluminum, so I am considering welding the pieces that broke. The pieces are small and will make a difficult job.

I have a mig welder with aluminum wire. I am thinking to try & build up the bore where the starter gearshaft fits.

I appreciate any ideas or thoughts on this. In the meantime I just look at my Bonnie. She sure is pretty.

Thanks,
Bonavent
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post #2 of 94 (permalink) Old 02-29-2012, 08:46 PM
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Do you have any pictures?
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post #3 of 94 (permalink) Old 02-29-2012, 10:25 PM
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There have been complete engines on ebay recently for $800 to $1100.

2005 Bonnie, Sleepers and Unifilter, AI gone, restrictor gone, Modre's peg kit, headlight & brake modulator, tach, NC wind deflector, gaiters, steibel, vmax mirrors, Hagons & Progressives, PIAA. http://TexasCoastGeology.com
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post #4 of 94 (permalink) Old 03-01-2012, 01:19 AM
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Pinwheel Cycles in the US sells there engines on ebay. I have bought 2 or three from them and they are fantastic good guys. Never had an issue.

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post #5 of 94 (permalink) Old 03-01-2012, 02:01 AM
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Originally Posted by manray View Post
Do you have any pictures?
These failures all look the same. Later engine cases have support ribs in the casting around the boss. It's rare enough a failure I'm just keeping my fingers crossed, but I may look into machining a collar to press fit on the outside of the boss when I get some free time. Best of luck to you, Bonavent. Sorry I can't help with any advice other than maybe consider taking it to someone with a tig if you have any doubts about welding it yourself. Be sure to weigh time/effort/possibly won't work vs. just getting a used engine. If you get a latter 865, swap your cams in Maybe talk to triumph first, as stated in some of the other threads, and see if they'll help out at least.

Failure pics from here: http://www.triumphrat.net/twins-talk...t-failure.html




Although it's small and not a close up, you can see the support ribs of the later casting in this pic from here:
http://i275.photobucket.com/albums/j...b/CIMG0993.jpg


Last edited by Verde; 03-01-2012 at 02:04 AM.
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post #6 of 94 (permalink) Old 03-01-2012, 03:41 AM
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Sorry about your misfortune. Can you provide any details regarding the event that caused it to break?
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post #7 of 94 (permalink) Old 03-01-2012, 03:27 PM
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Originally Posted by Verde View Post
These failures all look the same. Later engine cases have support ribs in the casting around the boss. It's rare enough a failure I'm just keeping my fingers crossed, but I may look into machining a collar to press fit on the outside of the boss when I get some free time. Best of luck to you, Bonavent. Sorry I can't help with any advice other than maybe consider taking it to someone with a tig if you have any doubts about welding it yourself. Be sure to weigh time/effort/possibly won't work vs. just getting a used engine. If you get a latter 865, swap your cams in Maybe talk to triumph first, as stated in some of the other threads, and see if they'll help out at least.

Failure pics from here: http://www.triumphrat.net/twins-talk...t-failure.html




Although it's small and not a close up, you can see the support ribs of the later casting in this pic from here:
http://i275.photobucket.com/albums/j...b/CIMG0993.jpg

Is it just me or does part of the broken bore look to be heat colored?
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post #8 of 94 (permalink) Old 03-01-2012, 06:19 PM
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I think the best way to repair the case is to pull the motor so you can set it up in a mill or boreing machine(it must be done stright and center or it wont work) bore the hole through the block,then make a new boss press it in the hole you bored .I would get another clutch cover its not work messing with.
The easy fix would be to buy a used motor off ebay for $850 to $1250.You can allso buy used cases on ebay but then you have to buy gaskets .If you do the cases you will want to make sure you leave the pistons in the bores when you pull them apart.
If it was me I would buy a used motor.I dont think you want to weld the cases with a mig welder better get a tig for that kinda of work .I have a 250 miller mig with a spool gun for alum wire and I wouldnt try it with mine.Way to messy and heat spreads to much.

Why do I feel young on my bike
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post #9 of 94 (permalink) Old 03-01-2012, 08:03 PM
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How many bikes has this affected? Is there a run of vins?
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post #10 of 94 (permalink) Old 03-01-2012, 09:38 PM
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its just kinda a hit and miss deal on the early years 790s

Why do I feel young on my bike
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