Question about engine timing on a bike motor

Having some starting issues on a new engine I installed. After some pit row discussions with others, I'm starting to believe I have a major timing screw up.

The motor is a Triumph 675, fresh rebuild by the last owner's race team. I kept my original electronics and Fuel Injection, just swapped the engine and head.

I did remove the head to make sure all was well, so i had to reset the timing. The shop manual states that all I need to do is match the lines on the cam sprockets, and match a marker dot on the cam chain gear from the bottom crank. Did that, and everything else as per the book.

Got it all wrapped up, but no start. Engine turns fine, but it'll just drain the battery trying to kick over. I did get a backfire once, so there must be ignition. I know I'm getting fuel as well, for I've seen gas in the intake ports.

One person suggested that I could have the timing off by 180 degrees. The manual seems to be pretty clear that if I line up the cams and crank gear, I should be good, but now I'm wondering. Is it possible to have the marks lines up and still be that far off from the timing?

I thought about just pulling the crank gear and just rotating the crank again till the mark comes around. This way, I don't have to drop the motor to get the valve cover off. But after some discussion, I learned that if i'm off, I could slam a valve into a piston Needless to say, I won't be trying that.

Any advice is always appreciated. I have a race in 2 weeks, and I'd rather not hand over my bank account number to a Triumph dealer :-(

 

Is there a chance you could've switched the intake and exhaust cams? I did that the first time I put my motor back together and was lucky enough not to cause any interference, but the engine definitely didn't run.

 

Mechanical setup sounds ok. Sounds like a ECU timing issue. Disconnect the cam sensor and see if it starts. Usually there's a failsafe where the ECU will try switching 360 degres until it starts. You'll get an engine code.

I don't know about Triumph but I have seen Yamaha's sensor having different polarity from one model year to another. If it starts without the cam sensor, either use the one on your previous engine or switch the polarity of the one you have at the connector.

Good luck.

 

I kept good record of the cams, but it's clearly possible that i have them swapped. I would think that a valve would hit a piston in that case.

In terms of cam sensors, how would a motor run without one hooked up? I would think that's pretty critical for the ignition.

 

did you line up the crank timing mark with cylinder one at power stroke? it may just be 180 out.

 

If the ones we used on our snowmobile did, I sure hope Triumph's can...

I didn't try to map things out but while I'm certain you can mistakenly swap IN & EX cams on a I4 engine without any damages, I'd venture to say it would be mechanically catastrophic on a I3 because of its 120 crank...

 

I have no idea, so I'm guessing it's possible. Again, the manual didn't seem this was worth pointing out. You'd think that would be a big deal, for they put all sorts of silly legal warnings all over the place.

So what you're saying is that the TDC must be upon pushing the #1 piston up to be true TDC?

 

You sure about that? you can NOT just put the crank where ever you want as long as the cams are aligned properly. Unless the crank is EXACTLY right, it is wrong.

 

Yea, I kind of get that. That shop manual states that the cam gears should line up at the same time that the crank gear marker lines up. Doesn't state anything about if the crank gear marker is in the up stroke or the down stroke.

I want to think that if i see the crank gear marker in place, that it is showing TDC. But obviously, this is only an assumption based on my limited knowledge of bike motors.

 

A crank marker as an industry STD, is always at TDC Cyl#1.

If you followed the shop manual procedure, your valve timing is Ok. Your problem is elsewhere.

 

that

 

Oem head gasket? Thinner or thicker? I'm not really sure swapped cams would be catasrophic though. I mean the lobes are pushing valves down before or after tdc on any pistons on the triumph because of it's firing order...right? I may be wrong but I thought it was 1-2-3. I can check my manual for some ideas tomorrow and check this thread.

 

Sounds like your timing to fire is 180° off. Either move the ignition to the other side so it fires on the compression stroke, not the cylinder flush and inhale stroke is back to TDC with the cam lobes faced in, not out. In other words, the spark happens twice. You just have the ignition out of phase 180. So, you have two choices to make. Machine up the engineering to the crank/to/ignition or move the cams out 180° so someone fires back on the compression [phase] stroke.

Happens a lot with the top end rebuilds installing cams.

 

If you're sure you lined up the dot on the crank with the casting mark on the cases, and if you're sure you lined up the cams correctly, (lines flush with the valve cover surface, pointing inwards) then you should have that right. The 675 does not have a cam position sensor, so the "180 out" thing does not apply here. Line up all 3 marks correctly and it should run. Plug in your Tuneboy and see if you have any codes.

BTW you don't have to drop the engine to pull the valve cover.

 

Well, one good thing about dropping an engine, you become a lot faster at stripping down the components when you need to. In less than an hour, I had the tank, airbox, FI unit, valve cover and side crank cover off :up:

Once off, I found the obvious, the chain slipped off a gear, and the marks weren't aligned Should have this all back together in alignment tonight to try again.

Thanks for everyone's help. Always a great source of advice on the forum.

JD: yea, didn't have to drop to motor to get the valve cover off. In fact, I was able to rotate the cam chain without taking the cam cage off. A bit of a pain, but less than trying to get the 12 bolts that hold the cam cage in. I just removed the lower crank cam chain bolt, removal of the tensioner and some creative effort.

I don't have a tune boy, so no way to decipher the codes. I was getting a error code 12 on the engine light (kit box engine codes are listed in the kit manual). #12 is a coolant sensor, which I replaced both the sensor and wiring harness for the sensor. Still get the code, but I have a feeling I'm not clearing the ECU correctly.

 

180 out vs. ignition timing does not need a cam sensor. Just think old style points then. That was the concept without thinking cam sensor. Want to diagnose, think old basics. Spark out of phase. And since it's out of tooth phases, you now need to check compression for valve to piston tag. Hope the pockets are deep or you just missed the piston going down as the valve opened at full lift.

Codes run down 2 or 3 other variables. So, water temp is tied in with the fan switch. See if the fan system is short to ground, wire out of connector, connectors not connected are the 3 basics like cam phasing 180 or phantom chasing over the net one toof off.

 

your lines all have to match up AFTER the cams are tightened up and slack in the chain is gone.

 

Yep, just made sure of that when I tore it back apart last night. They all lne up now.

But, I tried again with a new battery, and no go. Starter turns fine but so starting :-(

I don't have anything to read the codes, so it's
on with the two hour drive to the dealer.

As long as it's nothing major and I get it back in time, I'm not too worried. I needed a new map done anyway.

 

Got compression? "jumped" cam timing can be harmfull to the precious bits..

 

what he said. check compression, should be close on all cyl.
are the plugs fouled out?