2008 won’t idle, tried a bunch, weird issues

Hopefully the new throttle body will help answer the question of why the idle screw seems to have no effect on idle RPM.

johnkol wrote:

Hopefully the new throttle body will help answer the question of why the idle screw seems to have no effect on idle RPM.

Major update…

Got new throttle body in, just plugged it in without fully installing it, that TPS also showed 70.

So I just started hunting for anything loose or out of place and didn’t really find anything. I reset ECU, disconnected and reconnected battery, etc.

Old sensor just randomly showed correct values out of nowhere through the range. So I said screw it and tightened it down. Bike was still hard to start and needed throttle.

I then checked in CO mode and RPMs are still whack showing 5500 or something like that. I then checked charging at idle. Bike cranked with about 12 volts and went up to 13.5, which is still weak.

Still hard to restart as well.

Also during all this testing and while back in TPS mode, it was flickering between 18-21 just kind of gently bouncing around.

So the new throttle body, which came with its own TPS, also showed 70 at idle?

How did you reset the ECU?

When you say that the "old" TPS started showing reasonable values, is that the original TPS or the replacement you got? And was that old TPS on the old throttle body or the new one?

It seems that these results point to the ECU as the culprit; you said that you are getting a new ECU?

johnkol wrote:

So the new throttle body, which came with its own TPS, also showed 70 at idle?

How did you reset the ECU?

When you say that the "old" TPS started showing reasonable values, is that the original TPS or the replacement you got? And was that old TPS on the old throttle body or the new one?

It seems that these results point to the ECU as the culprit; you said that you are getting a new ECU?

Yes new one showed 70.

I didn’t do anything I haven’t done before. I unplugged it and looked at the pins.

Yes, original TPS was working fine. And old throttle body. Essentially no change to the bike. I disconnected and reconnected the battery a few times and it’s “good”. I did the same exact thing over the last week and the 70 never reset which is what makes this weird.

The TPS still bouncing between 19-21 is what has me puzzled though as it’s getting inconsistent power it would seem.

johnkol wrote:

So the new throttle body, which came with its own TPS, also showed 70 at idle?

How did you reset the ECU?

When you say that the "old" TPS started showing reasonable values, is that the original TPS or the replacement you got? And was that old TPS on the old throttle body or the new one?

It seems that these results point to the ECU as the culprit; you said that you are getting a new ECU?

New battery. Bike starts OK, hard to start and restart but seemed to idle fine and rev ok. Tried new ECU, not sure if it made any difference, RPMs are still wrong. Got solid engine light when trying to restart. For what it’s worth I tilted my lean angle sensor a bunch with bike running and it didn’t shut it down or throw any codes.

Did the TPS idle instability improve at all with either the new battery or ECU?

Since the bike can now hold higher RPMs, can you check the charging voltage to see whether you're closer to 14V?

Have you checked Diagnostic Monitoring Code 09 to see what it shows for the Lean Angle Sensor?

If you're getting a CEL, then the ECU should have thrown a Fault Code; can you see it?

johnkol wrote:

Did the TPS idle instability improve at all with either the new battery or ECU?

Since the bike can now hold higher RPMs, can you check the charging voltage to see whether you're closer to 14V?

Have you checked Diagnostic Monitoring Code 09 to see what it shows for the Lean Angle Sensor?

If you're getting a CEL, then the ECU should have thrown a Fault Code; can you see it?

The instability is kind of there still.

Doesn’t seem to store any codes.  Brand new battery is showing around 13.6 for charging, that’s with current rectifier and a new one I had ready to try.  I’m pretty close to pulling the trigger and parting it out.

So CEL is on but the screen does not show any Fault Codes? Does this happen with either ECU?

Is 13.6V at idle or higher RPMs?

johnkol wrote:

So CEL is on but the screen does not show any Fault Codes? Does this happen with either ECU?

Is 13.6V at idle or higher RPMs?

Sorry just seeing this. The CEL would just flash/flicker upon trying to start which from what I see might be normal.

13.6 was at idle

And lost my other message. I unplugged this and bike still ran, CPS? Shouldn’t be able to run per manual. Same for lean sensor. It will throw codes for some stuff like it I remove ignition coil.

Flynavy wrote:

I unplugged this and bike still ran, CPS? Shouldn’t be able to run per manual.  Same for lean sensor.  It will throw codes for some stuff like it I remove ignition coil.

No, the CPS connector is a grey cylindrical one; the other connector in that picture (with red and black wires coming out of it) is the Generator Coupler, but I cannot readily identify the one you're holding. Is it coming out of the crankcase? Can you pull back the sheathing a bit and see what colour wires are going to it?

13.6V at idle is perfectly fine; can you rev it up a bit and see what you get?

So CEL does not stay on after the bike has started?

johnkol wrote:

Flynavy wrote:

I unplugged this and bike still ran, CPS? Shouldn’t be able to run per manual.  Same for lean sensor.  It will throw codes for some stuff like it I remove ignition coil.

No, the CPS connector is a grey cylindrical one; the other connector in that picture (with red and black wires coming out of it) is the Generator Coupler, but I cannot readily identify the one you're holding. Is it coming out of the crankcase? Can you pull back the sheathing a bit and see what colour wires are going to it?

13.6V at idle is perfectly fine; can you rev it up a bit and see what you get?

So CEL does not stay on after the bike has started?

We are so beyond that, unfortunately in a fit of manic rage I said screw it I need to know what the insides look like.  I have an untrained eye but the cylinder walls looks fine.  Piston doesn’t seem OEM, assuming the previous guy put a cheap option in.  Valves look like valves?  Where the piston clips on has some exposed clip looking thing, not sure if normal.

The cylinder head looks really clean, the cylinder itself looks fine too, the piston does not look OEM (never seen those horizontal grooves before), but the rings look okay; I cannot see the exposed clips you mention, could you take a closer picture, or maybe point them out?

johnkol wrote:

The cylinder head looks really clean, the cylinder itself looks fine too, the piston does not look OEM (never seen those horizontal grooves before), but the rings look okay; I cannot see the exposed clips you mention, could you take a closer picture, or maybe point them out?

Definitely a 50.00 China piston, the clip I’m talking about is pictured in their stock photo so I’m not worried about it. So what’s next? Did I just do all of this for nothing? Because assembly is gonna be a nightmare and take me forever I’m sure.

You measured compression at 50 PSI, right? And when you added oil to the cylinder, compression increased, which points to piston/rings. The valves look good, although it's the other side of them that determines how well they seal against the valve seats; but given the absence of carbon deposits, it's unlikely that the valves are the problem.

OEM piston and rings are $150, so I think it makes sense to install them in order to eliminate any questions about the mechanical aspects of the engine.

johnkol wrote:

You measured compression at 50 PSI, right? And when you added oil to the cylinder, compression increased, which points to piston/rings. The valves look good, although it's the other side of them that determines how well they seal against the valve seats; but given the absence of carbon deposits, it's unlikely that the valves are the problem.

OEM piston and rings are $150, so I think it makes sense to install them in order to eliminate any questions about the mechanical aspects of the engine.

I wasn’t seeing them offered at that price so I’ll be looking. I can get a used cylinder and piston for 220 ish from my source, worth it to go that way instead?

Service Honda has them at that price, Rocky Mountain is a bit cheaper but their OEM parts are not linkable.

Used parts are a gamble; what do you do if compression still measures low? Do you suspect used cylinder/piston/rings, or do you focus your attention to valve seats/valve stem guides?

johnkol wrote:

Service Honda has them at that price, Rocky Mountain is a bit cheaper but their OEM parts are not linkable.

Used parts are a gamble; what do you do if compression still measures low? Do you suspect used cylinder/piston/rings, or do you focus your attention to valve seats/valve stem guides?

Fair point. So install a new piston, put it all back together and see where I’m at. I knew this needed to be done but wish it didn’t as I’m learning as I go. I strongly suspect something wire wise is out to lunch but finding it will be a pain in the ass. I think I need to get in the book and go sensor by sensor (which you probably told me to do on page 1).

I’ve spent roughly 2800.00 total on this bike so far. Do you think it’s worth the fight?

I suspect the same, that the root cause of all these electrical gremlins is one frayed wire that makes contact with the frame and messes everything up; as you say though, this is extremely difficult to troubleshoot, and the complete OEM wire loom is not even being offered for sale.

Is it worth it? I don't know. WRRs around here are always priced above $4500, so you're well below that amount. The unknown factor is how far away you are from a fully functional bike. If the new piston/rings solve the compression problem, will the engine run without issues, or will the electrical gremlins still make it stumble? On the other hand, how much can you get by parting out the bike, and how much more will you need to add to get a good WRR? Is that added amount worth your hours and frustration in fixing this bike?

johnkol wrote:

I suspect the same, that the root cause of all these electrical gremlins is one frayed wire that makes contact with the frame and messes everything up; as you say though, this is extremely difficult to troubleshoot, and the complete OEM wire loom is not even being offered for sale.

Is it worth it? I don't know. WRRs around here are always priced above $4500, so you're well below that amount. The unknown factor is how far away you are from a fully functional bike. If the new piston/rings solve the compression problem, will the engine run without issues, or will the electrical gremlins still make it stumble? On the other hand, how much can you get by parting out the bike, and how much more will you need to add to get a good WRR? Is that added amount worth your hours and frustration in fixing this bike?

Man… I just don’t know. Even if this fixes it, it’s still an ugly beat to hell bike. I just want to break even and make this bad dream go away.

If the bike is beat to hell, then even if you completely fix it for under $3k (which is doubtful), you won't be able to sell it for much more than that, and this just covers your materials cost, not the hours, frustration, and sweat you poured into this project.

Unless you were planning on keeping it in spite of its appearance, I would vote for cutting your losses and recouping as much as you can by parting it out.

johnkol wrote:

If the bike is beat to hell, then even if you completely fix it for under $3k (which is doubtful), you won't be able to sell it for much more than that, and this just covers your materials cost, not the hours, frustration, and sweat you poured into this project.

Unless you were planning on keeping it in spite of its appearance, I would vote for cutting your losses and recouping as much as you can by parting it out.

Just noticed this on the piston, all 4 “corners” have marks. What’s this mean? I heard tapping when engine ran but I know noises can mean so many different things.

It seems like the valves are hitting the piston! This could be happening for three reasons:

1. Incorrect valve timing, but you said you checked the timing and it is fine
2. Worn out valve stem seals/guides, which seems unlikely in a low-mileage motor
3. Incorrect valve cutouts in the piston, which is the most likely cause here because, as you said, this is a cheap chinese piston

Depending on how long this has been happening, it is quite possible that the piston has deformed the valves (or bent the valve stem, or worn the stem guides) resulting in the valves not sealing properly against the valve seats, which would produce the low compression you have measured.

It therefore seems that you need a new piston, but you also now have to check the valve seats, valve stems, and valve stem seals/guides. Unfortunately, these are not easy things to measure, and the safest route is to get new valves, seals, and guides, although guides are very difficult to swap.

Maybe you can just get a new piston and rings, see if compression comes up to normal levels, and if it does then don't worry about the valves.

johnkol wrote:

It seems like the valves are hitting the piston! This could be happening for three reasons:

1. Incorrect valve timing, but you said you checked the timing and it is fine
2. Worn out valve stem seals/guides, which seems unlikely in a low-mileage motor
3. Incorrect valve cutouts in the piston, which is the most likely cause here because, as you said, this is a cheap chinese piston

Depending on how long this has been happening, it is quite possible that the piston has deformed the valves (or bent the valve stem, or worn the stem guides) resulting in the valves not sealing properly against the valve seats, which would produce the low compression you have measured.

It therefore seems that you need a new piston, but you also now have to check the valve seats, valve stems, and valve stem seals/guides. Unfortunately, these are not easy things to measure, and the safest route is to get new valves, seals, and guides, although guides are very difficult to swap.

Maybe you can just get a new piston and rings, see if compression comes up to normal levels, and if it does then don't worry about the valves.

It’s worth mentioning if it hasn’t been before that previous previous owner put a WR250F piston in, meant for 5 valve engine, and damaged some stuff. Next guy said one valve was slightly bent, so he replaced it with the piston. Probably cheapest stuff he could find.

I’d love to check the valves it just seems tough. But a definitive answer would be nice for sure.