rear cylinder sucking in all the time
Thread Starter
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1st Gear
Joined: Jun 2010
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rear cylinder sucking in all the time
Has anyone ever seen this or is this normal. I'll explain everything I have done so far:
I bought an assembled CCI bike kit, it has an revtech 88 in it, the reason I bought it was to customize it the way I want it. I bought it cheap enough. The bike would sometimes skip and hesitate at around 3500 rpm under load conditions.
There is about 2000 miles on the 2003 engine.
I thought I would go ahead and change out some stuff I wanted to do with hopes it would solve the hesitation issue, plus I wanted to learn how to do it myself.
Replaced ignition and coil with twin tech single fire. Had a shop check the timing and it was okay.
I did things that shouldn't effect the way it was running, 6 spd tranny, primo belt drive.
It still hesitated so I messed with jetting the carb, makuni. I got it to run stronger but still had that stupid intermittent hesitation.
Had a guy tell me and show me that the rear exhaust is sucking in air, if you place your hand near the tip it did actually suck your hand in.
Okay so I started down the path that maybe the exhaust valve/adjustments were not right, I pulled the engine, pulled the head and had a shop go through it to make sure it was okay, it was. I replaced the solid pushrods with adjustable ones. Got it back together and it still sucked in.
I replaced the lifters, still sucked in air
I backed of the exhaust pushrod by 1/2 turn, still sucked air, I haven't tried backing it off any more.
Is this normal ??? I can not see how it would be.
Is it possible someone before me swapped out the cam with a wrong one?
Other question:
If I pull the rear plug wire it runs about the same, just a little bit different.
If I pull the front plug wire the engine stops unless I have a little throttle open.
Is this normal??
I have swapped plugs, and wires.
I know this is long but any input would be grateful.
Thanks,
Jim
Chandler Az
I bought an assembled CCI bike kit, it has an revtech 88 in it, the reason I bought it was to customize it the way I want it. I bought it cheap enough. The bike would sometimes skip and hesitate at around 3500 rpm under load conditions.
There is about 2000 miles on the 2003 engine.
I thought I would go ahead and change out some stuff I wanted to do with hopes it would solve the hesitation issue, plus I wanted to learn how to do it myself.
Replaced ignition and coil with twin tech single fire. Had a shop check the timing and it was okay.
I did things that shouldn't effect the way it was running, 6 spd tranny, primo belt drive.
It still hesitated so I messed with jetting the carb, makuni. I got it to run stronger but still had that stupid intermittent hesitation.
Had a guy tell me and show me that the rear exhaust is sucking in air, if you place your hand near the tip it did actually suck your hand in.
Okay so I started down the path that maybe the exhaust valve/adjustments were not right, I pulled the engine, pulled the head and had a shop go through it to make sure it was okay, it was. I replaced the solid pushrods with adjustable ones. Got it back together and it still sucked in.
I replaced the lifters, still sucked in air
I backed of the exhaust pushrod by 1/2 turn, still sucked air, I haven't tried backing it off any more.
Is this normal ??? I can not see how it would be.
Is it possible someone before me swapped out the cam with a wrong one?
Other question:
If I pull the rear plug wire it runs about the same, just a little bit different.
If I pull the front plug wire the engine stops unless I have a little throttle open.
Is this normal??
I have swapped plugs, and wires.
I know this is long but any input would be grateful.
Thanks,
Jim
Chandler Az
Road Master
Joined: Jul 2007
Posts: 1,009
Likes: 4
Does the engine have a nosecone ignition?
If so they are notorious for dropping the rear cylinder if in single fire mode.
If single fire, swap the ignition wires and the plug wires so that the coils will fire opposite. If the problem moves to the other cylinder you will then know it is the ignition.
Do the exhaust pipes have any baffles in them? The rear pipe is shorter and you may be getting exhaust reversion and contaminating the rear cylinder fuel with burnt gas.
If so they are notorious for dropping the rear cylinder if in single fire mode.
If single fire, swap the ignition wires and the plug wires so that the coils will fire opposite. If the problem moves to the other cylinder you will then know it is the ignition.
Do the exhaust pipes have any baffles in them? The rear pipe is shorter and you may be getting exhaust reversion and contaminating the rear cylinder fuel with burnt gas.
Thread Starter
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1st Gear
Joined: Jun 2010
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AJ
What do you mean by "nosecone ignition" Is this a product from twin tech?
I will try swaping the wires in the morning.
They are straight pipes but I did put in the anti reversion cones. What about the exhaust inserts that have a bolt welded across the opening? would they be better?
I'll update after swaping the wires.
Thanks
What do you mean by "nosecone ignition" Is this a product from twin tech?
I will try swaping the wires in the morning.
They are straight pipes but I did put in the anti reversion cones. What about the exhaust inserts that have a bolt welded across the opening? would they be better?
I'll update after swaping the wires.
Thanks
Road Master
Joined: Jul 2007
Posts: 1,009
Likes: 4
The ignition module fits in the cam cover just under the cap that is held on by two screws. Heat from the motor will cause it to fail. Other ignitions are mounted some where on the frame.
And the mention of the cam being off a tooth is a possibility.
I have seen no proof that reversion cones offer much help. Something needs to be in there to breakup the back flow of he exhaust. When the valve shuts a vacuum is created and gasses rush back into the pipe. Something should be in there to disrupt that and deflectors near the end of the pipe may be better.
And the mention of the cam being off a tooth is a possibility.
I have seen no proof that reversion cones offer much help. Something needs to be in there to breakup the back flow of he exhaust. When the valve shuts a vacuum is created and gasses rush back into the pipe. Something should be in there to disrupt that and deflectors near the end of the pipe may be better.
Thread Starter
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1st Gear
Joined: Jun 2010
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Okay, I undestand about the nosecone ingnition
I swapped the wires and it is still the back cylinder
I have to get a compression tester to check the rear VS the front
Just out of curiosity I took out the rear anti reversionary cone slit the sides a little and made the hole a little smaller at the exit side, I re welded it. Basically all I did was make the restriction a little tighter.
There was a noticeable difference in the throttle response when I rode it but it still sucks in.
I guess my next step is baffles or new exhaust if the compression is okay.
Any suggestions on what to use?
Again thanks for your input..
Jim
I swapped the wires and it is still the back cylinder
I have to get a compression tester to check the rear VS the front
Just out of curiosity I took out the rear anti reversionary cone slit the sides a little and made the hole a little smaller at the exit side, I re welded it. Basically all I did was make the restriction a little tighter.
There was a noticeable difference in the throttle response when I rode it but it still sucks in.
I guess my next step is baffles or new exhaust if the compression is okay.
Any suggestions on what to use?
Again thanks for your input..
Jim
Road Master
Joined: Jul 2007
Posts: 1,009
Likes: 4
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Outstanding HDF Member
Joined: Oct 2007
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From: El Cajon Ca.
Have you checked the compression? im not tryin to flame ya but those rev-techs are crap. Made in Korea.
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Thread Starter
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1st Gear
Joined: Jun 2010
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AJ,
Pipes are Samson rip saws.
I just dropped the bike off at the local shop, they have a great mechanic.
I'll let you know what they say.
BLKBAGGER
I know they are not the best - Don't have the money to put something better in it.
I think once it's certified by the locak shop I'm going to sell it.
Thanks
Jim
Pipes are Samson rip saws.
I just dropped the bike off at the local shop, they have a great mechanic.
I'll let you know what they say.
BLKBAGGER
I know they are not the best - Don't have the money to put something better in it.
I think once it's certified by the locak shop I'm going to sell it.
Thanks
Jim
Thread Starter
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1st Gear
Joined: Jun 2010
Posts: 5
Likes: 0
AJ,
Not sure if you can see this, as old as this is.
The shop said what I am seeing is normal for a short rear pipe, also said there could be a aftermarket cam in it.
The bike is running really good after they went through it to check my work, they adjsted the pushrods, they were a little off and then adjusted the timing which was also a little off.
Since the bike is running okay all is good, HOWEVER I am going to put baffles in it..
Thanks AJ - seems as though you were right on ......
Not sure if you can see this, as old as this is.
The shop said what I am seeing is normal for a short rear pipe, also said there could be a aftermarket cam in it.
The bike is running really good after they went through it to check my work, they adjsted the pushrods, they were a little off and then adjusted the timing which was also a little off.
Since the bike is running okay all is good, HOWEVER I am going to put baffles in it..
Thanks AJ - seems as though you were right on ......