Engine won't rev past about 4600rom

[Beau-Kat]

Perhaps this is the overkill of all overkill solutions, but have you considered taking your bike to a local dyno-tuner? I know we have at least 3 motorcycle specific here in Milwaukee...At least there you can get it up to speed and check off what's not causing the issue.

I'd continue to focus on that #4 cylinder...my checklist would start with #1 . Are the valve clearances in spec? #2 . Is your compression within spec? #3 . We're pretty confident you're getting fuel (sooty plug), have any of the jets within #4 carb been disturbed? Loosend up, fallen out, cross-threaded, mixed up, clogged (I know I'm reaching here). #4 . Can you get your hands on a known good TCI? Are you sure all electrical connections are solid on both primary and secondary side of the coil all the way to the spark plug?

We've already addressed the most common cause (diaphragms), we know it getting fuel (sooty plugs leads me to believe it's not a fuel delivery issue, doesn't rule out starvation, but I'd look elsewhere for now)....I'm just typing out loud here, so bear with me...OP stated it ran better with a new clean plug, albeit for a short time...only variable needed is compression.

 

Checked/cleaned all electrical connections having to do with engine running.

I just did the valve clearance inspection and serviced the carbs.

Only the exhaust valves for #3 needed adjustment.

Carbs really looked clean inside. Disassembled and checked all float levels, jets, and ports.

Checked all carb boots, hoses, synch port caps, etc. All look good. Sprayed WD-40 around them with engine idling. No engine operation changes perceived.

Unless I got something screwed up in the #4 carb, I don't know. I do have our two five year old boys coming and going from the garage, so can get distracted and possibly missed something.

Diaphragms should be here in two days.

[videoarizona]

Rusty,

This is a really interesting problem. I'm still puzzled as to what could cause the motor to not rev to full potential. If we had a set of points, I would say the points are bouncing at high rpm's....floating. Remember that well....My Austin Healey would ground out at high rpms...loose condensor. So what would be the equivalent today?

 

I'm following. Ready to learn...

[cowpuc]

My wanna swap the plug cap on 4 with one of the other plugs and see if the problem follows to that cylinder.. Just unscrew it from the plug wire. I have had caps go high ohm on me and cause really weak spark..

[garyS-NJ]

I read through your post because my bike doing similar.. from what I see in your post it looks like reseating the carb set cured your problem (you had an intake leak making you run way lean). for future reference, you can check for that with a bottle of propane and a hose to direct the propane gas at all connections. And I'd think with an intake leak making it run lean, it would then run better with choke but not sure if that would top out the RPM..

 

My bike which I bought seized after sitting for a while is idling but wont rev past 3500Rpm without popping out the carb throats and PAJ1 (and I think the main jet bleeds) and it bogs here too. I'm not through it yet (trying everything before pulling the carb set) but I did have problem with my sliders. they weren't sliding some were stuck.. I cleaned and lubricated the bores and that freed them up but they still were'n't snapping back the same and then used seafoam to lubricate and that got them all fluttering nice but one wasn't fluttering and I found the diaphragm would rotate on the slider.. I had read a post somewhere if that happens you can bond the diaphrams to sliders with RTV but I didn't see how to do it.. I could see that there was a gap where the diaphragm should be pinched between the plastic washers so I held the slide in my fist (first aligned the diaphragm) and tapped the center metal with a hammer to press it all together. hey members! are the sliders and diaphrams just pressed together>? this anchored the diaphragm and got ther slider fluttering while running.. (but I'm still not getting past 3500r's)..

[Beau-Kat]

My wanna swap the plug cap on 4 with one of the other plugs and see if the problem follows to that cylinder.. Just unscrew it from the plug wire. I have had caps go high ohm on me and cause really weak spark..

 

Only had enough time to install the new slide diaphragm on #4 slide today. I'll get the rest on tomorrow.

But, finally something is happening (or failing) that gives me some direction.

Now, I'm getting weak spark on 4 AND on 3. So, that's what I'm looking into now. Tomorrow, I'm gonna check spark again on 1 and 2.

All primary sides of ignition coils ohms are reading 3.2. Couldn't get my probes in there to check the secondary sides. Will get to that tomorrow.

All pick-up coils tested good at 115-120 ohms at all test points.

I bought these new NGK caps already installed on the new wires. The caps don't seem to wanna be unscrewed so I can test them. Don't wanna screw them up by using to much twisting force.

What should be a good ohm reading for a good plug cap?

Anybody had this issue and discovered a bad stator?

Also, if the TCI fails, wouldn't it just not spark at all on some of the plugs? Probably wouldn't get weak spark with a failed TCI, I would think.

[flyday58]

Read back thru the thread but don't see which TCI you are running, stock or Ignitech. Could have a bearing on the problem.

[videoarizona]

((What should be a good ohm reading for a good plug cap?))

 

 

From memory, each wire/cap combo needs to have a 5K ohm resistance to the plug. This is what keeps the original computer happy. When I bought my plug wires and caps...they were tested and showed 5K ohms. The wires are solid wires...no resistance there...so it's got to be in the cap.

 

 

 

[Beau-Kat]

((What should be a good ohm reading for a good plug cap?))

 

 

From memory, each wire/cap combo needs to have a 5K ohm resistance to the plug. This is what keeps the original computer happy. When I bought my plug wires and caps...they were tested and showed 5K ohms. The wires are solid wires...no resistance there...so it's got to be in the cap.

 

 

 

 

Yes, solid wires.

I disconnected the spark plug wire from the coil and read mine through the spark plug wire and spark plug cap. Showed 4.8K ohm

Secondary at the coil is 13K ohm.

[Beau-Kat]

Read back thru the thread but don't see which TCI you are running, stock or Ignitech. Could have a bearing on the problem.

 

I guess it's stock. Can't see any markings on it. But I haven't removed it, so I can't see all around it.

I did disconnect and check the two cables connecting to it. Ends and pins were very clean. Reconnected them, and now have very weak spark on #2 plug also. Seems it's all going downhill now.

[tankerman]

Check the intake boots between the carbs and cylinders. Its real easy to do get the engine running then spray some light oil at the boots if they are the culprit the engine will smooth out. This is a real common problem on older bikes.

[Beau-Kat]

Check the intake boots between the carbs and cylinders. Its real easy to do get the engine running then spray some light oil at the boots if they are the culprit the engine will smooth out. This is a real common problem on older bikes.

 

Thanks.

Already addressed that. I believe all that is good. Have narrowed it down to weak spark issues for sure.

[Beau-Kat]

I guess it's stock. Can't see any markings on it. But I haven't removed it, so I can't see all around it.

I did disconnect and check the two cables connecting to it. Ends and pins were very clean. Reconnected them, and now have very weak spark on #2 plug also. Seems it's all going downhill now.

 

I now know it is a stock TCI.

I didn't know what the Ingitech looked like, but did research on that unit last night.

[flyday58]

Ahh. Okay. I have to lean heavily toward a TCI-related problem. Myself and others have experienced issues like yours with TCIs with corrosion lurking inside, or corrosion down-line somewhere in the connectors keeping the TCI from getting the proper voltage to operate correctly. Mine had diodes that had turned to white powder. In your case, since the bike was stored inside before you bought it, and i assume since, I would scour the harness for a connector I missed that is corroded or has damaged wires. Any mice issues where the bike is kept?

[Beau-Kat]

All the connectors are ok.

 

I'm gonna pull the TCI out and see if it may be wet or corroded inside. Probably one or the other.

 

This bike has always been inside and in really good condition. But I do ride my bikes, rain or shine, so stuff gets wet. If I finish my rides at home, I wipe them down, and if the rain was particularly heavy, put a fan on them before I put them up for the night.

 

Note: After I serviced the carbs, adjusted the valves, and replaced the valve cover gaskets, I used 409 and garden hose pressure to wash all of the old drippy and filmy oil off the engine and chassis. Might have gotten into the TCI. Didn't know of all these TCI woes (especially that water could intrude into them) before I had this problem.

 

Learn a lot on the internet these days.

[Flyinfool]

Is there someone local that you can borrow a known good TCI from just for testing?

[Beau-Kat]

Is there someone local that you can borrow a known good TCI from just for testing?

I wish.

But I just moved here a couple of months ago and don't know any resources yet.

Jim (Blue Mountain) lives pretty close, but he doesn't have a 1st gen.

[garyS-NJ]

what was it??

[Beau-Kat]

Haven't gotten back to it yet.

 

I do have a 1998 Vmax.

Does anyone know if maybe I could swap that one to the Royale to test?

Or is that a totally different TCI?

[Beau-Kat]

O.K. Got my tci removed and opened up.

Looking inside, it looks great to me with no visible water intrusion or corrosion damage. But that's the side I can see.

However, I don't see how to remove the circuit board from the housing so I can flip it and view the components. I removed the center screw, but it still seems stuck.

I saw some photos on here of TCIs opened (and directions on how to carefully accomplish that) up but can't seem to find them now.

[Prairiehammer]

You can either cut the enclosure open (not preferred) or unsolder the connector (preferred).

http://www.venturerider.org/forum/showthread.php?86427-Peek-inside-my-TCI-if-you-will&highlight=unsolder+tci

[Flyinfool]

These boards are so old and fragile that I chose to cut mine open instead of desoldering and then resoldering the connector pins. Even though I have a lot of experience, training, and the right equipment to do the soldering, I still felt it was safer to cut the case.

I made my cut in the case about a half inch from the connectors. After I did the Diode replacement, As long as you are this far in you should replace the 8 diodes, I sealed the whole thing back up using electronic safe RTV. Not all RTV is safe around electronics, the ones that smell kind of like a salad have acid in them that can cause corrosion. The electronic safe RTV's do not contain any corrosive ingredients.

[Beau-Kat]

OK.

Haven't cut the cover off the TCI yet because I have a couple more questions.

Can a problem in the TCI cause weak spark? Or is it all or nothing, as far as spark goes?

If the TCI has failed, would I still have spark to all plugs or would spark be totally absent for one or more?

I do have spark to all plugs, but it is weak to at least two now.

Like I said before, I've ohmed out and tested all other ignition parts and connections (I think I got them all). All tested good.

[10spd]

I have a question for you. When y I ur bike acts up. Does your tach jump around?

[Beau-Kat]

I have a question for you. When y I ur bike acts up. Does your tach jump around?

 

I've seen where others had that happen when they had a TCI issue.

 

But I have never seen my tach jump around, and I've watched it closely since reading those posts.

 

Still looking for answers about whether a failed TCI will cause weak spark or just no spark at all for any cylinders.

[Beau-Kat]

Bump.

I know somebody on here has gotta know the answers to these questions...??