CDI UNITS FOR THE XT660!!!

[hb7]

Demark ...how hard are you pushing those rpms?

[DEmark]

OMC, I think alot like you, get the motor breathing good with new carbs and a can, then when its time for a rebuild, bump the compression and put a street cam in. Thats what I intended to do with my 03 Baghira, but I just don't have the time on my hands to build a motor now, and slightly used Baghiras are selling soo cheap, I just bought another bike and I got the 03 as a parts bike.

I hope you guys don't think from my signature that I am a dissatified MZ owner, quite the opposite, the MZs have outlasted the other bikes I have owned. I know there is much interest in what breaks and how reliable the motors are so I put my experience right in my signature.

Why do I think I have seen two rod failures? Well, I ride pretty aggressively, but I don't abuse the machine, I might bump up against the rev limiter once or twice each time I ride but I don't park the revs right there. I saw a guy on a Raptor once doing doughnuts all the time bumping into the rev limiter, he floated the valves and bent them with the piston- a stock motor too. BTW, I also have broke spokes in FOUR different rear wheels on my Baghira, further evidence that I ride my bike a bit harder than the average Baghira owner.

Some of you guys might disagree on this point, but I think that the Keihin fcr carbs and the m4 can I had on both bikes also helped shorten the life of the motors. I used to think that there was NO loss of reliabilty by getting the motor breathing good, but if you stop and think about it, it MUST be a factor in the life span of a motor, consider this equation:

bigger carbs w/accellerator pumps and a free flowing exhaust = more horsepower and better throttle response

more horsepower and better throttle response = more stress on the motor

more stress on the motor = shorter lifespan for motor

[DEmark]

continued: Do you see any fault in my logic there? The throttle response is VASTLY improved with the accellerator pump carbs, this has GOT to load everything in the motor and transmission more. You will see what I am talking about when you get the carbs on your bike. BTW, did you see my post "installing the FCRs" you might find it helpful.


HENRI! how many miles you got on your bike now??

[hb7]

I have ~32k miles....and I rarely go higher than 5500 rpm...
mostly 5000 rpm at cruising. The rear sprocket is a 39
which isn't very lively....but I get ~43-45 mpg.

On the other hand the stock baghira is quite lively with the stock 43 or 45 rear sprocket. I guess you never can get enough throttle response....

regards, Henri

[OLDMTNCARVER]

DEmark,
Thank you for the imput!
I'm in the mountains on the west coast and a linear power curve is a big portion of my thoughts.
Returning from the MotoGP at Laguna Seca this year I'd have to say that in frustration my Baghira saw some at the rev limiter moments. the carbs that had been jetted with a DynoJet stage one kit were not happy unless at high rpms.
The thought of FCRs are that they are known and can be refined with much more ease than an unknown carb.
In the mountains here I'm not running the engine at high rpms and a smooth range between 3 to 6K (I'm guessing) 6000 being at the outside and 5000rpms +/- probably more realistic.
Hugh grins with the stock exhaust and no jet kit, nothing but growls and bad thoughts since the modifactions.
I know that this is just a state of tune, but at the same time makes me wonder about the cams that might be ground in the future and refined is really big in my thoughts. H.P. is great. Torque is motivating...
Best to all,
OMC

[OLDMTNCARVER]

By the way. I'm looking to learn about things like lift, duration, overlap, degreeing and stuff like that...and wondering about a cams profile and the materials used. Cryogenics for the materials granular structure and its stabilization for durability...
When does an obsession become a sickness?

[Wonky]

When you enjoy being sick!!!!

[Wonky]

I have regularly tickled the rev-limiter in all gears on my stock motor and am happy to say i've had 120MPH from a stock engine with a G-Force system. It was hard getting that last 10MPH but a very very smooth throttle control eventually got me there. I have to say i was, and am, impressed with that! The motors completed about 2500 miles from new and is an 03 model. We had it here at the workshop for 3 years before i decided to have it, she had 18km on the clock and after spending the last few months playing i'm finally at the point of no return.

As DEmark has rightly said putting a set of carbs and a can on a stock motor WILL inevitably kill it. The amount of people that ask me "how much is a tune?" and i reply "how much ya got to spend?" For me i have waited untill everything can be reworked all together, do it right forst time and you shouldn't have any problems, ok you might have to tweak a little for a few days to find a happy medium with the settings but the engine will be strong, solid and ready to chew on the ass of anything else you find on the road, swallow it and spit it out behind it.

When you think these engines are around 40-47BHP standard and can be reliably tuned to almost DOUBLE the BHP it really does prove that these motors are strong, hardy thumpers. My only advice to anyone wanting to unleash the hibernating rabid panther is to save your cash or buy the parts, put them all on a shelf in your boys room and collect all the parts like an old Transformers collection, when you have the set then you can build a Tarmac Terrorist!!!! Big grins, never wanting to head home, guys stopping at traffic lights and asking "man what the hell is that?", now that's the stuff right there!

[OLDMTNCARVER]

Wonky,
Hey every time I ride or even look at the BP I know that I'm Waaaaaaaay past sick!!!
Hey get back to work on yours! Hope you cold's way gone, don't hurt yourself, Buddy!
OMC

[cat]

continued: Do you see any fault in my logic there? The throttle response is VASTLY improved with the accellerator pump carbs, this has GOT to load everything in the motor and transmission more.
...
HENRI! how many miles you got on your bike now??

hmmm...ok. It is a thumper, after all. High revs, high output generally means 4 cylinders - less reciprocating mass, in other words. The quicker response means more load on the conrod and bearings.

The modern high performance 4-stroke singles generally specify a rebuild time in hours - and they're race engines, anyway. It'll be interesting to see what the longevity of the new Yamaha 660 engine is.

DEmark, those engines of yours, it seems like quite high mileage - given the increased load, and you say you use it. 47,000 and 36,000 miles...let
s see...57,000 km (the 36,000 miles). That's not bad, I suppose. What do they do stock?

What I'm getting is that is what we need is a "spec" - Wonky, your guys can probably advise - what the expected small-end and big-end life is with a stock engine and what it is with higher revs. I doubt that it would be any better with the Carillo rod and bigger piston.

Your 47,000 miles / 75,000 km is not bad. (Keith, didn't you have a big-end failure quite early on, or am I thinking of something else?)

So...you could say change small-end bearing - if not big-end as well, which means stripping the motor - at about 40,000 miles / 64,000 km - make it 60,000 km, on a stock motor, to be on the safe side. (I'd make it 50,000 km.) And at 30,000 miles / 48,000 km with the FCR carbs. And that doesn't cover the big-end.
hmmmm

[cat]

I must check the Baghira specifications/alternative parts doc - what it specifies as the alternative CDI. If it's the 3VD one, it should come out, it's "unverified information". .........

...Yes, it says

Yamaha TDM 850 (3VD, not 4TX.)
(rev limiter set to 8400,
ignition advance earlier at 38° to 42°)

So, you say the rev limiter - 8400 rpm - doesn't actually work? That it results in there being no rev limiter?

[Wonky]

Wonky,
Hey every time I ride or even look at the BP I know that I'm Waaaaaaaay past sick!!!
Hey get back to work on yours! Hope you cold's way gone, don't hurt yourself, Buddy!
OMC

Yep the colds gone thanks to some seriously hot chillies, funny, my misses still has it after three weeks and i only had it 3 days, sweet!

CAT:

Your pretty bang on really. For a stock motor an oil change every 1500miles will be the key. We have regular customers that have hit 50 and 60,000 "MILES" before rebuild. It's really hard to say exactly when to rebuild. Generally if your getting in excess of 30,000 miles before part failure then your motors strong and well cared for.

If your running aftermarket exhaust, carbs, etc then you are looking around the 30,000 mile mark too. BUT! and it's a big BUT, it varies with different types of use, some-one that uses the bike for a bit of fun and a blast at the weekend will obviously put different stresses on components than someone that uses it every day of the week for trips to work, commuting, etc. It's really hard to say. Generally the XT motor is like a Tonka toy, pretty much bullet proof from stock. It's very unusual to have a motor in here that's completed less than 30,000 miles and has had some kind of component failiure. Tuned bikes obviously is a different story and depends on how the bikes treated.

One of the biggest causes of damage to the XT engine is not letting the engine warm up before you ring it's neck. One thing that's very common with these bikes is riders that "blip" the throttle, this obviously throws the piston up the liner with a ton of force and aggression and cause all kinds of damage further down the engines life. I myself used to "blip" the throttle purely as a bad habbit untill i was "told off" for doing it, thus why i now know and hence the reason why i have stopped doing it. I general slowly raise the revs to warm the engine, be gentle! It WILL help prolong the life expectancy of the engine.

At the end of the day if your tweaking the motor i would suggest regular oil changes, 1500 miles at the most, a strip inspection at 30,000 if it concerns you, if not then wait till it gives up the ghost and then deal with it. After all, wasting time and money stripping an engine that may well still be up for another 30,000 miles is a little silly.

Just take good care of your engine with all the usual service parts and you should be fine. My personal opinion is ride it till it dies but don't neglect it. Another good tip is to take the spark plug out and shine an inspection light down into the barrel, look to see if theres any gremlins lurking about or any "scoring" in there that could be causing damage. A simple inspection that could save you money in the future.

[Wonky]

I must check the Baghira specifications/alternative parts doc - what it specifies as the alternative CDI. If it's the 3VD one, it should come out, it's "unverified information". .........

...Yes, it says

Yamaha TDM 850 (3VD, not 4TX.)
(rev limiter set to 8400,
ignition advance earlier at 38° to 42°)

So, you say the rev limiter - 8400 rpm - doesn't actually work? That it results in there being no rev limiter?

CAT, just puit the CDI down, a very big hole, then walk away...don't question it, just walk away!!!

[cat]

ok, so you're saying is just don't increase the rev limit, whether or not it's only to 8400. or it exposes what is maybe one of the weakest points in the engine. although, yes, they are pretty much one of Yamaha's "bulletproof" engines.)
and if you put a bigger piston and Carillo conrod with it, the forces are higher, so still don't do it.

I think the best thing for the alternative parts doc would be to add a cautionary note to explain that raising the rev limit is not good, and that the only reason to use one would be if the stock CDI was unobtainable.

[cat]

Right. Agreed.
If you're going to do a strip inspection at 30,000 miles, though, you might as well put a new small-end bearing. (! That's assuming you meant strip as in top-end, not the entire thing!)

Oil changes. Like most of the "bulletproof" Yamaha/Honda singles (the little ones, especially, are more "bulletproof" - they don't have the great forces like the big ones), change the oil often.