No low speed spark on #1 and #3 '88 Vmax

[barber1303]

Strange situation that has me perplexed. My '88 Vmax will idle reasonably well, but it's only running on the front two cylinders. When you crack the throttle it stumbles a little, but then the rear two cylinders start firing and it rapidly climbs RPM. I've pulled each spark plug cap individually and actually watched it do this with a spare plug held against the cylinders. When they do finally start up, the spark is good, but under low speed conditions I get either nothing or very intermittent spark on the rear two cylinders.

Resistance through the primaries are at 2.8-2.9 Ohms. Secondaries are around 20 kOhms (through the caps). I'm measuring 11.8V at the R/W wires to the coils (engine on but not running...12.3V at the battery). Battery is new and when running, I'm getting 14.4V at the battery at idle speed.

I've swapped the plugs/caps/wires with known good running parts (from my '85) with no significant change.

Any thoughts on what else to check?

 

[Fire-medic]

Are the spark plug wires at-all greenish-in color at their ends, where they attach to the plug caps? Have you tried cutting about 3/8-1/2" off the plug wires?

If I understand you, the front cyl's are firing at idle, the rears are NOT. That suggests to-me, plugged idle jets in the jet block. If you don't have the correct mixture of fuel/air, it won't ignite. Once you get past where the idle jets are metering fuel, then the main jet and its needle are controlling the mixture. Now it is in the correct mix-ratio, and the cyl's start firing.

 

[barber1303]

Firemedic, thanks for the response. To answer your questions:

I pulled the plug wire spades from the connector housings and cleaned them on the coils. I "unmounted?" the spark plug wires from the coils and cut as small section from them to expose fresh copper and reinstalled them ensuring good contact was made. I verified good connections by measuring the resistance through the coils circuits. All checked out. As an additional diagnostic step, I also took the wires/caps from my '85 and mounted those as well, to no effect.

The carbs that came with the bike had been freshly rebuilt and were immaculately clean. I have since pulled these carbs (as a diagnostic step) and replaced them with the carbs I rebuilt for my '85. The problem persisted, so I do not believe it is a carburation issue. I can see that the rear cylinders are not sparking around idle speed, but will start sparking once the throttle is opened and the engine speed increases. I don't believe this is a combustion issue, but specifically a spark issue.

Thanks for the continued assistance!

Chris

 

[Pighuntingpuppy]

Doesnt that bike have multiple pickups? Maybe one or more are failing.

 

[barber1303]

Doesnt that bike have multiple pickups? Maybe one or more are failing.

Working on checking those now. Thanks.

 

[02GF74]

Motorcycles use wasted spark ignition ie coil fires also on exhaust stroke and correct me if I'm wrong, I understood vmax to do that. I'm pretty certain there are two coils that each fire one pair of cylinders but I don't know which coil for which pair.

If you find that the pair of cylinders correspond to the same coil, the rat coil is suspect _ dud you try swapping coils round or from a different bike.

If that fails, try swapping out the ignition module.

 

[barber1303]

Just spent a sweltering couple hours in my hot garage checking the entire ignition system and everything checks out per the specs in the manual. Ingnition coil resistances, pick up coil resistances, spark plug wire resistances are all to spec. I pulled all the connectors from their housings and cleaned them and checked continuity through the wiring harness...all fine. Once I reassembled and started it up, it was EXACTLY the same as before. Will start and idle on the front two cylinders and will kick in the rear two cylinders once the engine RPMs get above around 2000RPM.

I'm stumped...think it could be the TCI module?...

 

[barber1303]

UGH!!! Guys, I think its the TCI. I swapped in the TCI from my '85 and the problem went away. I'm going to switch back for good measure...tough to be sure you've got it mastered unless you can turn the problem off and then back on again.

 

[barber1303]

Back and forth several times...problem follows the '88 TCI. Guess I'm in the market for TCI...they're cheap and easy to find...right?

 

[Traumahawk]

Yes they are.....and you can even go aftermarket. Sean Morley is the man for those.

 

[Fire-medic]

I was going to-ask 'what year is your bike?' The '85-'89 has 2 pick-ups. Since you switched-out the CDI and it worked, I think you found it.

I have one-more suggestion: try opening the box, and re-soldering the connectors from the plugs to the printed circuit board (on the PC board). See what happens. It costs nothing and it may cure your problem. People have used this technique to fix VBoost control boxes and engine CDI boxes on the VMax.

Sean Morley should have the Ignitech engine spark control (CDI) boxes, which have advantages over the stock ignition boxes, as they can also control the VBoost. I think they have a rev-limiter too.

 

[one2dmax]

Cheap no, Easy to find (stock good used no but new aftermarket yes). I have ignitech units on hand.

 

[Toronto Giant]

I just joined today after finding the answer to my latest problem in this post. I purchased a non-running Vmax in June that sat in a garage for the last 2 years. After doing the basics like new battery and plugs, oil change and a once over everything I got it running, but not for long as the fuel pump went. 2 weeks of waiting, then first chance I got, I installed the fuel pump and rode for 1 day. The next day it wouldn't start. The intermittent problem I was having with it starting was now permanent. This is when I figured out how to remove my rotor to get to the starter clutch.

After many delays I was finally able to get the bike back together and synchronize the carbs. It was running beautifully for about a week then the intermittent problem of it bogging to 2000 rpm, then taking off like a rocket came back. The last day I rode it the rpm just kept getting higher before the 2 rear cylinders would kick in. After 85 miles it was boggy until 5000 rpm, then rocket mode. I thought it was only one cylinder, but when testing coils by switching wires I discovered that both rear cylinders had no spark. That's when I asked the google and it brought me here. After checking all connections were clean, I'm sure it's the ignition box. I've already inquired with Sean Morley, so hopefully I can get this sorted out soon, as riding season is approaching the end in Toronto.

 

[Fire-medic]

I just joined today after finding the answer to my latest problem in this post. I purchased a non-running Vmax in June that sat in a garage for the last 2 years. After doing the basics like new battery and plugs, oil change and a once over everything I got it running, but not for long as the fuel pump went. 2 weeks of waiting, then first chance I got, I installed the fuel pump and rode for 1 day. The next day it wouldn't start. The intermittent problem I was having with it starting was now permanent. This is when I figured out how to remove my rotor to get to the starter clutch.

After many delays I was finally able to get the bike back together and synchronize the carbs. It was running beautifully for about a week then the intermittent problem of it bogging to 2000 rpm, then taking off like a rocket came back. The last day I rode it the rpm just kept getting higher before the 2 rear cylinders would kick in. After 85 miles it was boggy until 5000 rpm, then rocket mode. I thought it was only one cylinder, but when testing coils by switching wires I discovered that both rear cylinders had no spark. That's when I asked the google and it brought me here. After checking all connections were clean, I'm sure it's the ignition box. I've already inquired with Sean Morley, so hopefully I can get this sorted out soon, as riding season is approaching the end in Toronto.

I hope your CDI replacement fixes things.

Here in so. Florida, we're soon going to see the influx of Canadian cars and motorcycles, and sales of smoked meats and poutine will skyrocket.

 

[DreamV4]

Back and forth several times...problem follows the '88 TCI. Guess I'm in the market for TCI...they're cheap and easy to find...right?

Paid $120 from ebay shipped including tax.
Open ign module and check transistors. you have to cut plastic. I used drimel with fiber cut off wheel. I had 2 burnt transistors, find my thread if you want.
you can buy and replace transistors.

 

[02GF74]

I purchased a non-running Vmax in June that sat in a garage for the last 2 years.

thought it was only one cylinder, but when testing coils by switching wires I discovered that both rear cylinders had no spark.

1. It is quite common for the jets to get block after a period of non use (less then 6 months for me) so maybe worthwhile servicing the carbs.

2. The rear pair of coils are easily accessible, not so the front ones. Did you use all 4 coils for your test = trying to eliminate bad coils vs bad ignition unit.

 

[DreamV4]

I can sell you coils. I tested them(bench test), I got spark. No cracks.

 

[maleko89]

Don't discount the p/up coils. Your '88 has a one for cylinders 1/3 and one for 2/4 up front.

Normally they either work or fail but strange things can happen.

Mark

 

[DreamV4]

Don't discount the p/up coils. Your '88 has a one for cylinders 1/3 and one for 2/4 up front.

Normally they either work or fail but strange things can happen.

Mark

it should have 4 pick up coils, 5 wires, going to pick up. There are no 360 degrees cylinders. Each cylinder gets wasted spark.

 

[maleko89]

There are four individual circuits, but two coil boxes. One is for front cylinders, other for rear.