Engine "jumps" in the middle of heavy acceleration

I am back again with another question for the KZ gods. The other night I was out riding the KZ1000 and gave it full throttle a couple of times. Two out of three times, in second gear and under full throttle, the engine acted as if I pulled the clutch for a split second around 5-6k RPMs. It happens so quick, and goes right back to pulling through the powerband. I don't feel like it could be the clutch slipping, as its an instant on/off type of feeling.

Last month I had problems with the carbs and got that issue straightened out, but still need to sync them. I thought maybe a cylinder was dropping, but I also wonder if I could have something wrong in the transmission as well. Sometimes the bike will get hung up between gears and act as if it is in neutral when accelerating hard. I'm not sure if this is my fault or something in the transmission. It also makes a clunk shifting down into first, but it has done that the four years I have owned it.

Any ideas? Valve clearances are in spec, coils are one year old Emgos, new plugs and wires, added a relay to put power to the coils, and timing was in spec just a few weeks ago (points, not electronic).

If not an issue with ignition or carbs, might help to perform a clutch push rod adjustment.

Good Fortune!

What type of engine oil being used?


Best Oils To Use In Your Bike (Just My Opinion)

Engine oil : The commercial grade oils are clearly superior to the mass market oils. For the best protection in your bike or car, use Shell Rotella Synthetic, available at Wal-Mart in blue containers . For the best petroleum oil you can buy, get Shell Rotella T, Mobil Delvac 1300, or Chevron Delo 400, available at any auto parts store. On the back of most oil cans is a circular stamp with the certification. Avoid oils that say "energy conserving" in the bottom half of the donut.

These oils contain friction modifier additives that could cause clutch slipping over time. The EPA mandated certain gas mileage, so the auto makers turned to the oil manufacturers who came up with friction modifiers of the oil to meet these new standards. All XXw-20 and XXw-30 oils are energy conserving, and should not be used in your motorcycle. Don't buy any oil additives like STP or Slick-50. Here's several listings on all about oil justifying these conclusions.

The Recommended Synthetic Oils :

Shell Rotella Synthetic
5w-40 Delvac 1 Synthetic
5w-40 AMSOil AMF Synthetic (pricey, but it’s your money)
10w-40 Golden Spectro Synthetic
10w-50 Motul 5100 Synthetic
10w-40 Mobil-1 Synthetic
15w-50 Mobil-1 MX4T Synthetic

The best synthetics are: (in no particular order)

Shell Rotella-T Synthetic 5w-40 (blue container is synthetic, not white which is dino), gallon at Wal-Mart.
Mobil Delvac-1 5w-40 (grey container is synthetic, not black which is dino), gallon at Petro stations, gallon at Farm and Fleet.
Mobil-1 SUV 5w-40, qt anywhere.
AMSOil AMF 10w-40 synthetic motorcycle oil. (again, pricey)
Golden Spectro Supreme, (no price).
Motul 5100 Ester, (no price).

Mobil-1 automotive oils all contain small amounts of moly - about 100 to 200 ppm. This can cause clutch slippage in some motorcycles. I've only heard of this being a problem in Honda Shadows.


The Recommended Petroleum Oils

Chevron Delo 400 15w-40
Delvac 1300 15w-40
Shell Rotella 15w-40

The best petroleum oils are: (in no particular order)

Chevron Delo 400 15w-40 (blue container) gallon at any auto parts store, gallons at Costco.

Mobil Delvac 1300 15w-40 (black container) gallon at any auto parts store, gallons at Sam's Club.

Shell Rotella-T 15w-40 (white container) gallon at Wal-Mart or any auto parts store, gallons at Sam's Club.

Castrol 15w-40 (Green container) gallon at Wal-Mart or any auto parts store, gallons at Sam’s club.

Chain and sprockets are in good condition and chain is properly adjusted?

My 77 jumps out of gear like that also except mine does it in third gear. I am lead to believe it has something to do with the shift forks or possibly a bent shaft? i dont know for sure tho, never tore it apart to look.

Second gear dogs are worn causing the gear to slip out of engagement under heavy throttle application. This is the reason for undercutting the second gear dogs for performance builds.

In my opinion, you need to check the other stuff that has been suggested first. Start with the cheapest and easiest thing first. Make sure that the clutch is properly adjusted. Proper oil used, etc.

toadson wrote: ...was out riding the KZ1000 and gave it full throttle a couple of times. Two out of three times, in second gear and under full throttle, the engine acted as if I pulled the clutch for a split second around 5-6k RPMs. It happens so quick, and goes right back to pulling through the powerband. I don't feel like it could be the clutch slipping, as its an instant on/off type of feeling...
coils are one year old Emgos, new plugs and wires, added a relay to put power to the coils, and timing was in spec just a few weeks ago (points, not electronic).

don't feel like it could be the clutch slipping, as its an instant on/off type of feeling --- might be an intermittent disconnect in the wiring somewhere between the battery positive and the dual connector feeding battery positive to both coils. Perhaps in the added relay circuit.

Could attempt to duplicate the condition while idling in neutral, by manipulating and wiggling the associated wires and connectors.

If a clutch lock-out switch is involved, would assure that it's not an issue.

Would also assure integrity of the ground connection where the negative battery cable attaches to the rear of the engine.

The culprit might be any electrical condition that intermittently interrupts power to the coils. Which could also include some imperfection in the points ignition. It's the opening of the points that un-grounds the coil and causes the coil to fire. While closed, the points are supposed to provide a path to ground from the coil's primary winding.

If not already done, would service the points (set gap, dress contacts as needed, and clean).

Good Fortune!

Thanks for all the good suggestions. I am running 15-45w Rotella T (non-synthetic). I didn't even think about the chain jumping a tooth, so I will start there first. Hopefully tonight I will have a chance to check the chain and take the bike out for a ride and report back.

This is absolutly CLASSIC worn second gear. Second is the most likely one to do this also.

I was able to check the chain and it was looser than it should have been, but nothing to be alarmed about. I took it for a drive before tightening it up and gave it plenty of chances to slip, and only had it happen three out of maybe 12-15 times. I noticed it happening the most when in second gear and giving it full throttle from 2500-3000 rpms, and having it "jump" right around 4000 rpms. It only happened in second gear again.

I tightened up the chain and only got about 6 or 7 tries in, and it pulled with no problems. I wouldn't say the problem is fixed just yet though. This bike always tricks me the first time i ride it after working on it. I just can't believe I didn't think to check the chain in the first place.

I took a picture of the teeth on the rear gear. I would say it is worn some, I just don't know how bad is too bad. I have some store credit at a motorcycle shop and am thinking about converting to 520 chain and sprockets.

If it were me, I'd either be doing the conversion, or replacing both sprockets and chain.

Sprockets And Drive Chains
www.sprocketspecialists.com/ (not sure if they are still in business)
www.sunstar-mc.com/home.aspx
www.rebelgears.com/
www.pmpsprockets.com/
www.schnitzracing.com
www.jtsprockets.com
www.pmfronline.com/counter_shaft_sprockets.php
www.dgchassis.net/

And www.gearingcommander.com for sprocket ratio's, if you're thinking of changing sprocket sizes.

The sprocket may last a while longer, perhaps for life of the existing chain, then replace both simultaneously.



Good Fortune!