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Beginning to restore an '83 VR. Some questions for the Gurus.

venturesome
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venturesome

venturesome

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I am restoring a 1983 VR. I just rebuilt the carbs and started it up. It ran OK until warmed up then starting running like $#$@$#! The problem seems to be ignition and I am checking that out now. The #2 and #4 cylinders are cold relative to the #1 and #3 . (also the tach doesn't work now, which makes sense).

My question is what is a normal temperature for a warmed up running engine at the exhaust ports? #2 and #4 show about 170 deg and #1 and #3 show about 450 deg. I am measuring temp with infrared sensor "gun" with laser pointed on pipes coming out of exhaust port. Should they all be around 450 deg or is this low or high?

Thanks for your help!

Prairiehammer

Prairiehammer

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Posted
I am restoring a 1983 VR. I just rebuilt the carbs and started it up. It ran OK until warmed up then starting running like $#$@$#! The problem seems to be ignition and I am checking that out now. The #2 and #4 cylinders are cold relative to the #1 and #3 . (also the tach doesn't work now, which makes sense).

My question is what is a normal temperature for a warmed up running engine at the exhaust ports? #2 and #4 show about 170 deg and #1 and #3 show about 450 deg. I am measuring temp with infrared sensor "gun" with laser pointed on pipes coming out of exhaust port. Should they all be around 450 deg or is this low or high?

Thanks for your help!

 

Since I don't have any way to measure the header pipe temperature, I cannot say what is a normal temperature, BUT I do know that the front chrome header pipes are double walled. That might account for the difference in temp.

However, since it runs like crap AND the tach doesn't work, then the wiring to/from the pickup coils and TCI or the connections on the TCI or the TCI is suspect.

cimmer

cimmer

Posted
Posted

have you tried to sync the carbs since you rebuilt them or adjust the idle mixture screws. I would look at those issues before looking at the TCI unit. Make sure all the vacuum line are properly seated and not leaking. I always look for the simple things first before jumping into the major items..

Good luck

Rick F.

zagger

zagger

Posted
Posted (edited)
I am restoring a 1983 VR. I just rebuilt the carbs and started it up. It ran OK until warmed up then starting running like $#$@$#! The problem seems to be ignition and I am checking that out now. The #2 and #4 cylinders are cold relative to the #1 and #3 . (also the tach doesn't work now, which makes sense).

My question is what is a normal temperature for a warmed up running engine at the exhaust ports? #2 and #4 show about 170 deg and #1 and #3 show about 450 deg. I am measuring temp with infrared sensor "gun" with laser pointed on pipes coming out of exhaust port. Should they all be around 450 deg or is this low or high?

Thanks for your help!

 

If you load the engine at all, it will become pretty obvious if all the cylinders are firing with a full charge of gas/air. I made notes in my service manual when I rebuilt my carbs several years ago - as far as I know, the enrichment circuit is not shown in the Yamaha XVZ1200 service manual cross-sectional drawing of the carb internals. When the engine was first started, you probably had the choke activated which has the effect of adding additional gas through the enrichment circuit. As you release the choke, less additional gas is provided and the engine may stop firing on any cylinders which are not getting an adequate supply of gas/air from each carb. I would imagine that you will find a problem in one or more carbs with the normal gas/air flow when the enrichment circuit is turned off at the handlebar. I will assume that you went through the various diaphrams in every carb, checking for cracks, etc. Proper operation depends on all the rubber diaphrams being in good shape.

 

I'm ignoring the spark question because it seems like the engine runs ok when cold (choke probably ON).

 

Good luck!

Edited by zagger
dingy

dingy

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Posted

Normally I see close to 300F or more at the head/pipe junction.

 

450 is really high, I would guess these cylinders are running lean.

 

Gary

zagger

zagger

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Posted
I bought a $20 infrared temp measuring device from radio shack this past Christmas for a stocking stuffer. It seemed to work.

 

Seems like an interesting idea. But I just looked online and it seems that the max. temperature that device can display is 230F. Is that high enough for a warmed up engine? I would have guessed that the exhaust pipe temp would be higher.

venturesome

venturesome

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I'm still confused about the temperatures. Front two cylinders seem too low, and back two seem two high. The airbox is off and I can view the sliders. They move only slightly when throttle is opened. Should they move significantly?

Maybe I have a combination of problems. The fact that the tach works OK when cold, then "drops out" when warmed up is also a concern. From what I read, that means #2 is not firing.

I didn't put new diaphragms in when I rebuilt the carbs, and they certainly weren't perfect, so maybe I will start there. Have to save up for 4 of 'em. No more ice cream for awhile!

zagger

zagger

Posted
Posted

The diaphragms actually run the carbs. They make the sliders (vacuum pistons) move along with the attached needles. If they have holes (quite likely in an older bike) then they won't do their job. Your description seems to indicate that the carbs are unable to supply the necessary gas once the enrichment circuit is off (choke off). Looking at every component made of rubbery stuff (like the diaphragms) would make sense since they do gradually crumble away over the years. Of course, making sure the carb internals are not full of crud would also be a natural thing to check. Good luck.

Prairiehammer

Prairiehammer

Posted
Posted
The fact that the tach works OK when cold, then "drops out" when warmed up is also a concern. From what I read, that means #2 is not firing.

 

The preceding comments regarding the carbs are valid, but the key diagnostic is the tachometer dropping out. This indicates an ignition issue, first and foremost. My opinion is that the TCI is defective. As the TCI warms, it is failing. No matter how dirty or defective the carbs are, the carbs will not cause the tach to quit.

zagger

zagger

Posted
Posted
The preceding comments regarding the carbs are valid, but the key diagnostic is the tachometer dropping out. This indicates an ignition issue, first and foremost. My opinion is that the TCI is defective. As the TCI warms, it is failing. No matter how dirty or defective the carbs are, the carbs will not cause the tach to quit.

 

True enough. If the tach stops working and the engine starts running rough at the same time (regardless of choke position), then I also vote for TCI problems since that is where the tach gets its signal from. It should be fairly simple to determine if the spark is absent on the questionable cylinders. If the rough operation when warm is determined solely by backing off on the choke and can be reversed by increasing the choke (thus every plug is obviously firing), then I vote for gas issues since the choke affects only the gas (and the tach operation may be an unrelated issue). Perhaps I'm not completely clear on what action causes the rough running - backing off on the choke, or simply warming up. The original posting of the problem doesn't clearly identify cause and effect - at least for me.

venturesome

venturesome

Posted
  • Author
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Thank you for your responses. Dingy's response of his experience with temps leads me to believe that I indeed have two problems:

One that two cylinders are not firing when engine is warmed up with choke off. (Low temps on #2 and #4 and tach driven by #2 is not working). I did check plugs for spark before starting engine and all 4 were firing. I did not check plugs for spark after engine was warmed up, but I will now and report results.

Two is that rear cylinders are too hot, suggesting a lean condition (maybe diaphragms not opening slides properly?).

I am repositioning the TCI to the top of the airbox and will open it up and check inside.

This will hopefully eliminate one of the potential problems.

I know the diaphragms need replacing, but I wanted to see if everything else checked out before taking that step. Carbs were thoroughly cleaned and I replaced all o-rings.

Prior to cleaning the carbs, I checked the compression. All cylinders were 145-150 cold. Also pickup coils and ignition coils checked OK.

This is an 83 VR that I picked up for $100, so I don't expect it to run great without a lot of headaches! The odometer shows 21000 miles, and I believe it to be accurate. The bike doesn't look heavily used, just badly neglected.

I appreciate the help from forum members who have been there, done that.

  • 1 year later...
venturesome

venturesome

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OK.. 16 months later and I am back to the '83. Plugs are now firing 1 and 3 only. No spark on 2 & 4. I have opened up TCI and it looks bad (see pic). I checked the diodes with my Harbor Freight multimeter and believe it or not they all seem to be OK! However, as you can see in the pictures, a couple (or more) of the capacitors? are corroded on top. Also I re-soldered the connectors. Coils and pickups check OK.

It looks like I will be quadrupling my investment soon!

My problem is how to obtain a replacement TCI. I haven't seen any posts from Dingy in the last few months, so I guess he is not selling the Ignitec anymore.

Anybody have a known good 83 TCI for sale or loan? (I would pay deposit). I can also use 83-89 and modify vacuum port.

Has anyone purchased a Ignitec direct from factory and if so, how much and are you happy with it? What was the delivery time?

Thanks!! I couldn't tackle this without help from forum members.

 

83TCI.jpg

bongobobny

bongobobny

Posted
Posted

Ventuesome, there was another recent thread that brought out another manufacturer of replacement TCI's but not sure if they have one compatible with '83. Of course you could always reroute the vacuum line coming from the boost sensor to manifold vacuum instead of carb vacuum and use '84 thru '89...

bongobobny

bongobobny

Posted
Posted

I looked at that one, but one BIG problem, the '83 is NOT directly compatible with the '84 and '85!!! Yes, you can make an '84 thru '89 work on an '83 if you change the vacuum line from the vacuum boost sensor from the carbs to the intake manifold. These vacuums are 180 degrees out of phase, the vacuum advance will work backwards using an '84 TCI on an '83, or an'83 TCI on an '84

snyper316

snyper316

Posted
Posted

well here is response i got back from the guy

 

Hello,

Yes we do have the replacement CDI for yourmotorcycle.

Its $367 shipped. We are currently having some issues with our website, so if you would like to order one, please give us a call at the number below.

Best Regards

 

Toll-Free number: (877)239-4390

 

On Mon, Jul 11, 2016 at 1:04 AM, Regulatorrectifier.com wrote:

Hello,

 

The part on the linked page below has a 3 year warranty. We need the number stamped on your factory unit. Please put it in the checkout notes when the order is placed.

 

The Vacuum port is no longer needed.

 

 

Best Regards

 

 

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