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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> TTR cams misaligned - from new!
Post Info TOPIC: TTR cams misaligned - from new!
matador


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TTR cams misaligned - from new!
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 I put up an earlier post 'TTR running a bit rough'. I brought my 07 Black rimmed TTR with 3k on the clock last March, but it really ran rough but the engine sounded ok. I stripped the carb and cleaned/ retuned it plus new plug and vac out the plug hole and clean the cylinder plug seat as the engine was missing under load, now all sorted?

Basically the bike would tic over ok, run ok but had an intermediate running problem, compression ok, I stripped the carb down again but no change. To me from engines in the past, if it's not external then it must be inside the engine, I assumed it could be valve clearances (I have known WR250 only start on kick, which had reduced clearances, my TTR would start ok).

I carefully removed the cam cover and inspection covers to start checking cam timing first but noticed the cams when set in the line had the wrong letters showing; Exhaust - I and Inlet - E. I carefully checked the clearances and they were within spec. With the inspection covers never being removed (they always get marked) and the cam sprocket bolts torqued correctly, I now felt sure the engine had been assembled wrong from new. I carefully reassembled the cam sprockets and the little bike started as well as ever but this time warmed up and ran ok with no intermediate running problem. I have only been for a short ride - off when I have finished writing this.

Before it was the worst trail bike I have ridden, ok I had a 40 year gap but to me a trail bike should have good low speed pickup for control - unless you are a ' teenager on a crosser', Now it has it's low speed control and is a joy to ride, I can now see why the last few owners sold it.

On a separate note, a friend in Oxford said he had a TTR from new and it always backfired when switched off, the dealer told him, 'they had checked it but nothing was wrong', it resulted in damaging x2 starter motors and trashed a few starter clutches - so he sold it.

More of an update than edit.

I took the TTR out for a 30 mile ride, totally different bike. After warming it up I gave it an uphill load test and it nearly clocked 70, much more power & louder induction noise. I tried it out on some trails and again the low speed control was there, instead of riding like a 'Plonker on a Fizzy' I'm well pleased.

Now I can see why TTR's are so popular, I put down the symptoms just in case anybody else has the same problems, even if you are not into fixing bikes at least you can take it to somebody who knows and ask them to check cam timing ID sprockets.

Out for a Wiltshire weekend now the bike is ready, BBQ organized at the back of a pub - one problem heavy rain forecast, well this is Springtime.

-- Edited by matador on Monday 13th of May 2013 08:24:39 AM



-- Edited by matador on Tuesday 14th of May 2013 07:47:43 AM

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Lin


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Interesting. Just to note, the TTR inlet cam and exhaust cam have the same Yamaha part number and therefor the same lobe profiles. So it can't be a case of mixed up cams. Must be a case of mixed up sprockets?

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matador


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Hi Lin, It would be easier to show the picture from a Haynes manual than explain on setting the cam sprockets. Correct me if I'm wrong but the cams are the same - inlet cam lob  facing backwards and exhaust facing forwards, with the crank on TDC (it can move back, so I held it in place with a socket tied to the cylinder). Now for the fun part, both cam sprockets are the same with 2-sets of lines on them. The front sprocket should have its E showing with a line parallel with the casing, and the same for the inlet with the I line parallel - so it's easy to get it wrong, if you don't speak English on an assembly line in Japan on a night shift. With a life time of engineering I can tell if something has been tampered with and this was from new.

I say the odd bit is it ran at all, the clue is the poor low speed pickup suggesting a crab jet problem. It's one of those faults that can happen from new, even the first time I looked at the cams, they lined up ok , but on closer look with the wrong letters showing - couldn't believe it as I was about to strip the carb down yet again.

Tip if you do remove the cam chain and remove the tensioner it needs screwing back inside as it will break something if you try and force it back in.  

 

I'm off today to the Wiltshire weekend, with my 'running like new' TTRbiggrin



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TTRfan


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Done it myself - see copy of my post below taken from my first project thread disbelief

Brian

 

The engine is nearly run in now so I have been giving it a bit more throttle only to find I had a misfire when opening the throttle wide. If I backed off then things would sort themselves out. Nevertheless, very frustrating!

It seemed to be carb related and I tried 3 different carbs each giving slightly different results but ultimately didn't solve the misfire.

So I swapped out the coil/HT lead, CDi and fitted a new spark plug. No improvement.

I seemed to be left with two possibilities - either valves or the ignition pick up.

I chose the easy option first which was to check the valve timing. I lined up the timing mark on the flywheel and took the cam cover off and was surprised to find the camshafts were one tooth out disbelief

Timing out.jpg

I corrected that and the TTR runs better than ever. 

I really can't explain why the fault coz I am meticulous in checking the camshafts are correctly aligned when rebuilding engines confuse

Brian



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matador


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Cheers Brian, Yep similar symptoms and I was going to ask you if you had a spare carb to try. I though it was close valve clearances affecting valve timing, hence the strip down. In truth I nearly missed it stripping down, so I would have gone through the problem and been none the wiser. I still say it was from new as anything the previous owners touched left some evidence (can't swear on hear) and with the cam chain off it's easier to check the clearances and they were all the same ).001" inside the tolerances if somebody had adjusted them they wouldn't be so accurate and the motor has only done 3k miles so why touch it?

Mine is a later model with Black rims, so the problem may be found on a sample of bikes from that latter batch.

I noticed from your picture that the crank had slipped back - I solved it with 'country boy' technology - piece of bale string tied to the socket bar to hold it on TDC.

Thanks for the quick supply of spares.



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