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The TTR250 FAQ web pages -> TTR250 -> Show us your bike! -> TTR conrods do bend . . . slightly
Post Info TOPIC: TTR conrods do bend . . . slightly
TTR250Raid


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TTR conrods do bend . . . slightly
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Perhaps 70mph is a little fast for TTR250 Raid.

18 November 2011, 6:15pm my birthday, A45 dual carriageway, 70ish mph, bit of a mechanical bang, automatically pulled in the clutch and freewheeled as far as possible. Hmmmm? Starter nice spin . . . Hmmmm started pushing.

At home bit of a hole in rear of left crankcase under starter motor. Engine out, no problem getting flywheel off, bolt loose, woodruff key sheared off. Head off, barrel off, Hmmmm piston comes with it! Conrod a bit bent.

So, only damage seems caused by broken conrod breaking piston, and barrel and crankase and exhaust valves and a few gear teeth.

Plenty oil, everything else turns smoothly. What do you reckon?



-- Edited by TTR250Raid on Thursday 19th of January 2012 12:52:13 PM

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truslack


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Ooo bugger, what has caused that? :S

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TTRfan


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If the oil is still in it and it turns over smoothly I reckon you should get another few thousand miles out of it biggrinbiggrinbiggrin

Worst I had seen before yours was where an engine had been run with no oil and it seized resulting in a bit of piston breaking off and dropping down to jam between the crank and balancer gear. This resulted in the balancer gear poking its head through the crankcase. Nowhere near as interesting as yours blankstare

What you gonna do - rebuild the engine?

Brian



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Cubber


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I think it was more than likely that the TTR was glad to be leaving Birmingham and environs and was humming to itself in gay abandon. aww

I think the key was sheared in the shaft as soon as the rode broke and as the shaft stopped quickly the flywheel momentum and torque came into effect.

Maybe 70 mph was a tad fast? bleh

Martyn



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TTR250Raid


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I reckon the conrod for whatever reason broke and flailed around a couple of times causing the damage and yep momentum sheared the woodruff key. Can't find any other damage not caused by it.
Piston skirt is cracked but still free in bore and bore is smooth, liner has damage at bottom, few teeth missing and balancer has a few scrape marks.
Looking for another engine that will fit or I can modify to fit.
Was coming out of Northampton towards Wellingborough.
If anyone wants more images I can send you some.
Thanks for your comments.
Hoping to move permanently to Devon at some time so look forward to all those green lanes.
Chris

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Livotlout


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Hi Chris,

 

Sorry to hear about your troubles, had similar with a 660 Yam engine in my MZ Baghira, the con rod decided to shake hands with the balancer gear.

Have you checked the right side of the engine (drive side), it looks like the balancer shaft is out of sync with the crank?

Best wishes with finding a new lump.

 

Alec.



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TTRfan


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truslack wrote:

I'm still intrigued as to why this has happened - a conrod shouldn't just snap through over-revving! I hope this isn't a general picture of how fragile TTR engines are!

Don't fret! I have stripped down a few TTR engines in my time and I would say that they are over engineered e.g. I am sure the main bearings would be strong enough for a tractor engine!

I am not sure that it is possible to over rev the TTR engine as I thought there was a rev limiter built into the CDi confuse

If I am pushing on with my TTR and taking it to the limit, the engine seems to top out and then its time to change up a gear wink

We await the verdict as to the cause. Normally engine damage is caused only by lack of oil but that doesn't semm to be the case here unless there was a blockage or the oil pump packed up? The latter is very unlikely I know.

Brian 



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truslack


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I'm still intrigued as to why this has happened - a conrod shouldn't just snap through over-revving! I hope this isn't a general picture of how fragile TTR engines are!

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TTRfan


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This may be the most cost-effective repair - http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=140685083557&ssPageName=ADME:B:SS:GB:1123#ht_500wt_1202



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Cubber


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There's no mention of it having/not having a kick starter.

It looks as if may be from a white tank model too????

Martyn



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East Budleigh. Devon
TTRfan


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The OE engine unit is a straight swap for the Raid engine. If the old motor had a kick start then, assuming it is undamaged, it can be fitted to the replacement no problems wink



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Cubber


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Then the missing sprag clutch could also, presumably, be swapped over confuse - a complete heart transplant with additional minor surgery. 

Martyn



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TTRfan


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Cubber wrote:

Then the missing sprag clutch could also, presumably, be swapped over confuse 

Yep - the sprag is the same on all TTR250 models from '93 to current date biggrin



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