yamaha 450 makes no power

[VTMotorsportsTuner]

VTMotorsports just received our first used 2006 Yamaha WR450 for our 2012 car. This is our third year running this motor with the Motec M400. I recently tuned the engine on our engine dyno, modifying an existing map we used before. I ran several dynamic pulls, and the motor is only making ~30hp and ~22 lbft. This is WAY off from what we know the 450 should produce, pulls on our motors from years before are ~54hp and ~32 lbft. I tried everything I could think of from a tuning standpoint and even brought in our 2010 engine tuner/team leader to help me. We reviewed all the engine logs and even ran some of his old 450 tunes, and each time we still made around 30 hp and 22 lbft. Does anyone have any ideas what could be causing our new (used) motor to be losing so much power? I'll do a leak down test and tear it down to try to find the problem but I wanted to see if anyone had any experiences like this. thanks!

[VTMotorsportsTuner]

Preliminary leak down testing shows no compressed air loss out of intake/exhaust valves. A very small amount of compressed air was coming out of the crankcase, but that could have been because the engine was cold. more to come, any comments help.

[Chris B]

personally if you're confident its not the tune, id start looking at mechanical elements and the simple ones first. check this top gear clip out, http://www.youtube.com/watch?v...3zH8&feature=related (http://www.youtube.com/watch?v=IiXfuvy3zH8&feature=related)

theyre trying to make a renault avantine as fast as an evo. james may recoupes 50 Hp of lost engine power over night just by giving it a thorough mechanical service. things like spark plugs, gaskets, heads, rings, valves, etc. not sure if you've tried this already or not but may be something to consider. if not, its still a funny top gear clip http://fsae.com/groupee_common/emoticons/icon_smile.gif

[VFR750R]

Make sure ignition timing is what you think it should be, verify the crank trigger is the same tooth count with the same gap as your other engines.

To verify timing without a timing light you could start by subtracting timing and see if the power goes up or down. What to do next should be obvious. I would recommend verifying timing mechanically with your trigger wheel if at all possible to avoid running the engine much with improper timing.

I'm not sure if all your other components are the same, but to make the same amount of power, you should be using the same amount of fuel. Verify things like fuel pressure, proper voltage to your injector(s), etc.

Poor voltage to your coil, or a poor ground could also significantly reduce power output even if the engine appears to have the right timing with a timing light.

If the timing is off, the fuel injector timing will also be off the same amount, which will also affect power, which could be the rest of any difference if you get your ignition timing right.

[Rex Chan]

If all the readings coming from the engine seem ok, maybe it could be your dyno reading funny? As in, something has changed in how your dyno reads torque/power, so the results will be off. Does the engine sound the same as it usually does? Hope this helps.

[Mbirt]

On a Youtube video of VT's 2010 car at MIS, I asked "Why only 32hp?" Got no response.

This video, Yamaha WR450F Dyno Testing Compilation (http://www.youtube.com/watch?v=ZBvYe0ip5Og), shows 51hp with the stock carb and a touch over 40 restricted. Did they ever get it up to 54hp restricted or is that an unrestricted? I can't remember how exactly I discovered it made 32hp at MIS in 2010, but it definitely stands out in my mind.

If lambda readings are kosher and the spark map is anywhere close to stock, I'd turn my attention to the cams, intake, and exhaust. If you're comfortable with it, sharing your plenum volume, intake tract I.D. and length to the valves, I.D. of the first step of the exhaust, and length from the exhaust valves to the first major geometry change (whether it be a muffler or FMF Megabomb-like device that I saw in VT's "2011 Teaser" video) might help us detect what's shorting your setup by 10-15hp. A copy of the recent power/tq curves would help too.

[VTMotorsportsTuner]

timing is fine, crank trigger, ref/sync settings, etc. are correct. i always verify timing is correct with a timing light. fuel map is similar to maps used that made power, so i know that's not the problem. poor voltage to the coil could be a problem, batter voltage was slightly low, but could that result in a ~45% power loss?? also verified that dyno is reading correctly.

[VTMotorsportsTuner]

in response to Mbirt:

I was there for the 2010 MIS competition. What you're thinking of is when we made ~32hp at the wheel on the chassis dyno at MIS. Our engine made 54hp at the crank on our engine dyno. yes, we had terrible drivetrain loss, something our 2012 car is addressing. leak down testing showed air coming out of the crankcase even after the engine is warm, so i'm going to replace the rings with new ones, we have another jug, should i replace that too even if the stock one looks ok? also, the intake and exhaust are ones that we used last semester to make over 50hp, so i know they are correct.

[Drew Price]

I'm with Rex, are you sure your dyno is calibrated correctly.

Before you pull the top end apart, did you actually check the compression, or just leakdown? A little air past the rings is normal.

Same exhaust and intake as you used on your other engines?

[Kirk Feldkamp]

Is the method you're making your pulls with the same as previous years? I've seen it happen way more than once that someone makes a pull in say 2nd gear and the dyno indicates a very low power output. If they then stick it in 5th or 6th gear, all of a sudden they make the power they were expecting. For any dynamic tests, the RPM rate of change during the pull can make a big difference in indicated output.

If all else fails, you could always throw the engine from last year back on just to confirm that all of the hardware (both engine and dyno) is still working the way it did last year. Then it would just be a process of elimination as you swap pieces over one by one.

I've gotten used engines on eBay before for karts, and I've learned that it is never ever a good idea to assume that it's been assembled correctly, or is in great shape right out of the box. Personally, I end up going through any engine I buy 'used' before I ever run it. I've destroyed a couple now under the assumption that the person that sold it to me knew what they were doing.

[revolutionary]

Any chance you can put your old engine back on the dyno to verify? If you are running the same type engine as before it should read the same.
Break it down to the basics.
Fuel? what kind? Fresh? egt/o2 read correctly throughout the pulls?
Spark? strong or weak? locked or timing curve? sparking at right time?
Compression? compare cranking compression to factory specs. How much is the leakdown? should be well under 10% even for a used engine. A good warm engine should be ~4-8%

[dazz]

Like Kirk said, you shouldn't assume that the used engine is assembled correctly. If everything else has checked out as identical to your previous setups, I'd be looking at cam timings. 1 or 2 teeth out on the sprockets and the thing can still run. I vaguely recall that that might have been one of the differences between the first gen YZ vs WR 400's and that you could move one of the cams on the WR a tooth for a more YZ like power delivery?

Turns out my memory isn't too bad! Here, I found it:
h t t p : / / motoman393. thumpertalk. com/ tech/ yztime. html

Anyways, my point is to check that all the valves are opening and closing when they are supposed to. And just because it runs, doesn't mean that they are correct.

[Drew Price]

Originally posted by dazz:
Like Kirk said, you shouldn't assume that the used engine is assembled correctly.


Even the big boys make mistakes. Late-90's and early 2000's Volkswagen 2.0L N/A AVG engines were often assembled at the factory with the piston rings installed upside-down, which gives a little higher oil consumption (tapered sealing rings) but compression is fine. Lots of bulletins out there that VW says up to 1.0 litre of oil consumption per 1000 miles driven is considered 'normal'.... but they also replaced a lot of piston / ring sets under warranty for people who complained.

That being said, make sure your measuring equipment and bolt on stuff is working like you think it is.

If you're sure it is, then tear in.

[js10coastr]

You're obviously missing the stickers on the side, those are worth about 5 hp each http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Adambomb]

Personally I've never been too hot on leakdown tests, typically you get the same results you have listed, which goes as far as telling you "the valves seem to hold air, and the crankcase leaks air."

Much better to do at least a cranking compression test, that will point you in the right direction as far as cam timing. Again popping the cam cover off and checking the timing marks is a must. Also you can check the condition of the rings by adding a few drops of motor oil to the cylinder: if the cranking compression goes up noticeably, your rings are worn.

I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."

[t21jj]

Originally posted by Adambomb:
Personally I've never been too hot on leakdown tests, typically you get the same results you have listed, which goes as far as telling you "the valves seem to hold air, and the crankcase leaks air."

Much better to do at least a cranking compression test, that will point you in the right direction as far as cam timing. Again popping the cam cover off and checking the timing marks is a must. Also you can check the condition of the rings by adding a few drops of motor oil to the cylinder: if the cranking compression goes up noticeably, your rings are worn.

I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."

Actually we could not even get him to do that. So Steve and I went and got a compression tester and tested it ourselves when he was not working on it. God that semester sucked so bad.

[dazz]

Originally posted by Adambomb:
"snip"
I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."

Just be a little careful doing this, for example, our KTM's have an auto de-comp that bumps the exhaust valve to bleed off some of the compression. (leaving enough for it to still start - sometimes...) KTM did this to allow them to use a much smaller battery and starter motor on their bikes. We did a cranking compression test and promptly pulled the head off to see what was wrong - nothing. We also tried disabling the auto de-comp only to find that the little starter motor isn't up to the job of cranking without the help of the de-comp.

I've just had a look at a parts fiche for the 06 WR450 and can see a similar system on the exhaust cam as is used on the KTM, so keep that in mind. There's also the possibility that the de-comp weight is jammed and the auto de-comp is not retracting once the engine starts?

[t21jj]

Originally posted by dazz:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
"snip"
I remember the first year we had a YFZ 450, the guy we bought if from claimed it was a "solid engine," fresh rebuild, etc., but we couldn't even get it to start. Our engine team leader at the time completely trusted the random dude on the internet he bought it from, and claimed that engine was a "sure thing." Then we finally convinced him to do a compression test on it and it made like 30 psi. More like a "sure turd."

Just be a little careful doing this, for example, our KTM's have an auto de-comp that bumps the exhaust valve to bleed off some of the compression. (leaving enough for it to still start - sometimes...) KTM did this to allow them to use a much smaller battery and starter motor on their bikes. We did a cranking compression test and promptly pulled the head off to see what was wrong - nothing. We also tried disabling the auto de-comp only to find that the little starter motor isn't up to the job of cranking without the help of the de-comp.

I've just had a look at a parts fiche for the 06 WR450 and can see a similar system on the exhaust cam as is used on the KTM, so keep that in mind. There's also the possibility that the de-comp weight is jammed and the auto de-comp is not retracting once the engine starts? </div></BLOCKQUOTE>

It does have a de-compression system and we checked with a local builder before checking the engine. A later rebuild of the engine confirmed the issues with the engine.

[bachelong]

Hey guys I was wondering if anyone had a cad model of a yamaha wr450. We're trying to get away from tearing the engine out of last years car to get measurements, so any help would be great.

[Mbirt]

Hey VTMotorsportsTuner, any updates on what you figured out with the weak engine? The Momentum article about your 2012 effort states that the engine was taken to 500+ cc. I'll assume that it made more power after a rebuild, but I've seen my team make 35hp to the sprocket after it was decided that building it to 511cc was the way to go. Volumetric efficiency is a perfectly suitable replacement for displacement.

[mmw2753]

I took over where he left off, I don't remember anything specifically wrong with it but I think a rebuild fixed the problem. 2012 had a 502 cc kit installed on 2 engines, but during a high speed aerodynamic testing day, the wrist pin sheared, the piston nailed the head, and the connecting rod went through the front of the crankcase. We ended up competing with a 450 cc engine which did very well. We dyno'd the 502 cc and got 53 hp (6800 rpm peak) and 43 lb*ft, the 450 cc was 54 hp (8500 rpm peak) and 37 lb*ft. Our engine dyno setup uses a sprocket adapter to a short VW axle, we haven't tested on a chassis dyno.

[Mbirt]

Thanks for the response. It's good to have this thread go full-circle.

In this case, there was no replacement for a reduction in displacement http://fsae.com/groupee_common/emoticons/icon_cool.gif

[Simon Dingle]

Originally posted by mmw2753:
We dyno'd the 502 cc and got 53 hp (6800 rpm peak) and 43 lb*ft, the 450 cc was 54 hp (8500 rpm peak) and 37 lb*ft.

Did you measure fuel consumption? I'd be interested to see if you improved BSFC by reducing the operation speed of your engine?

[mmw2753]

I don't have anything on hand. This year we are using a 450 cc engine for other reasons, so I didn't look into it. I could ask a volunteer to do some digging and see if they come up with an answer.

[Mbirt]

What do you suspect the limiting factor in the system was at 502cc? BMEP was still over 200 psi at the 6800 rpm power peak. Did it fall on its face hard or hold flat power to the rev limiter? I can see a stock 07+ WR head and cam combination doing this.