So confused, 1996 VFR wont draw in enough fuel into engine

this may give you some clues
CV Carb Tuning Procedures

 

Why do you say I don't listen? If it wasnt for you or Donald and a few others, my VFR would have never seen 9000 RPM. I got the bike to see 9000 rpm. Before, it could never see over 5500 rpm and that was with severe hesitation and then it would cut off. Seriously it was flat dead at 5500 rpm then it would just stahl out. Now at least it can go pass the 5000-6000 rpm and if I let it, I could easily red line it. It could never do that before. But since I listen to you and few others the bike is 90% there. Thank you for your help. I really do appreciate it. My wife appreciates it too because I have spent too much time in the garage ever since her brother gave me his bike.

At cruise the bike is perfect, it was not like that before I did the extra work. Was it the ultrasonic cleaning, the slow jets, or the valve adjustment that made it 90% better? I say it was the ultrasonic cleaning. You, Donald and few others made me pause and take a look back to see what could go wrong to a bike that sat for 5 years. I listened and got the ultrasonic cleaning done.


HRCH

 

Thank you, much appreciated. This helps a lot.


HRCH

 

Congrats! Bringing an idle machine back to life that has sat for a while is always interesting.

Not to be a pessimist, but have you tried to adjust the chain yet? The rear wheel eccentric can be problematic when they sit for a while. There are several threads about the trials and tribulations of getting them to be cooperative.

 

Thank you for your support. I actually did adjust the drive chain. It seemed to have no problem to adjust the chain. This bike has 30K miles on. The chain seems to be ok. I'm intend to get a second opinion. But so far I can't say the chain needs to be replaced. I can't even say for sure if it has the original chain.

HRCH

 

Was that one out of spec valve loose or tight?
Was it the exhaust valve or intake valve?

 

Maybe the first ones got ruined with a piece of wire or paper clip?
I agree I wish he would tell us WHY he replaced them.

 

The valve clearance that was off specs was #2l cyl inner intake valve. it was .11mm. It had a 1.92 shim in it. I had to increase the clearance two steps down. So I put a 1.88 shim in its place. I then swapped a few intake shims to increase the clearance on two other intake valves cyl 2 and 4 outer valves that were still within the + or - .03. However I thought that if I can get all the valves to measure dead on specs just by swapping a few shims I figuired what the heck just do it. When done all the intake valves were dead on specs. So the valves that I adjusted were too tight. Why did I replace the idle jets? Simply because even after i cleaned them they still looked corroded. I did not think the bike could idle better but it does. So with a more steady idle I found it much easier to sync the carbs. Im going to ride the bike around to see if the hesitation at 5000 to 6000 rpm will get better. But heck at least the bike can get past that flat spot and rev past 9000 rpm. As I said before I did the extra work the bike could not go over 5500rpm without cutting off. Thank you for your support. HRCH

 

Well, Guess What?............It looks like I got it. The hesitation at 5000-6000 rpm has been resolved. You all may not agree as how I got it resolved, but I really had no choice but to install jet kit as I did not know how to richen the 5000-6000 rpm fuel mixture without a jet kit. Before I say anymore, the bike does have a Two Brothers Racing slip-on and rear pipe that was installed by my brother-in law. I replaced the stock 125 main jet with a 128. I also replaced the stock needle jet with the needle jet that came with the jet kit. I installed the C clip in the 3rd position as recommend by Factory Pro. The bike now accelerates very strong especially at over 5000rpm. The bike will accept full throttle at around 4000rpm while in 2nd gear. When I accelerate past 5000rpm in 2nd gear and open full throttle my head will feel like it's pulled back. The torque of this V4 is insane. It's not as powerfull as my 1998 ZX11 Ninja, but it definettly feels like it has more torque in the mid range than my fuel injected 2009 ZX6R.

Is it perfect, no it's not? I get a little pop when I decel. The bike also at times will back fire during a moderate rpm upshift and wont happen during light rpm upshift. It does not happen all the time. I would more call the up-shift back fire a pop as it only happens one time and mostly from 2nd to 3rd gear. Not so much in 1st to 2nd gear. It wont pop more than one time during shifting. So if it pops from 2nd to 3rd, it wont pop again from 3rd to 4th. I could probably live with it, but I went this far, it would be great not to have it at all.

Also on another note, I would like to thank everyone who replied to my post as it was extremely helpful. I know I owe the members of this forum a special thank you for helping me take a step back and see what I had to do to resolve the issues from a bike that had sit for 5 years. Thank you to all. Am I a mechanic, no not anymore. I used to work on cars for a living but that was 10 years ago. Bikes are new to me so forgive me if I sometimes ask or do things that don't make any sense as I am doing my best.

Thank you HRCH

 

The new needles with 5 position clips used to be standard with all japanese motorcycles. Now we have to buy them. Sad.

BTW each notch on the needle is about .030 raising of the needle.

 

Even if you have the $100.00 certificate, (comes with jet kit), and they do ANY adjustments it can be $300.00 instantly.

 

I just checked the paper work that came with the Factory Pro jet kit. I didn't see any certificate.

My wife and I rode the VFR for about 1 1/2 today through some back roads. Even with the two of us on the bike I never once felt any hesitation. I accelerated in 1st and 2nd gear into 9000rpm with the two of us and the bike felt strong. Even with two people it still pulls very hard in 2nd gear.

Now if I can only get the exhaust pipe pop or backfire (what ever you want to call it) fixed I will be completely satisfied. I payed more attention to the exhaust pop on our run. It seems the backfire is light but can happen more than once. It will only happen while up-shifting moderately to high RPM (over 5000 rpm). I can prevent the back fire by not closing the throttle too fast when I shift. In other words don't shift too fast and it will not backfire. I have no idea if the light back fire at that higher RPM is caused by a too lean or too rich fuel mixture. As I said if I shift slower and not close the throttle too fast everything will be ok even in the higher RPM range 6000+.

When I have time this week, I'm going to mess around with needle clip position. I'm pretty sure the main jets I installed are the correct size because the bike pulls very hard and will accept full throttle at 4000rpm while in any gear.

HRCH

 

When this bike was given to me by my brother in law, my wife and I agreed not to put more than a $1K in it. With the new tires I'm already over the $1K. I already have two other street bikes and my family and I own 4 ATVs which requires regular maintenance. I took this project on because 1. I couldn't see a bike just sit when the owner no longer wanted it. 2nd, my father in law wanted to toss it in the junk yard. I knew I could get it running. I just needed to keep the cost low. This VFR is in pretty decent shape for a 15 year old bike with 30K miles on it. I'm truly impressed to see a bike that sat dormant for 5 years run so well.

As far as putting the bike on a dyno, I could get a price and see. I do however have a 130 main jet I could toss in. But first, I'm going to read the plugs while I have the 128 main jets in.

I'm reading mixed reviews regarding back fire, some ppl say it's from unburnt fuel exploding in the exhaust, which would be rich, some say it's a mixture that is too lean. So I'm really not sure. As I said, the back fire is light and does not happen all the time. I guess only a dyno test will reveal the true fuel mixture.



HRCH

 

backfire in exhaust on overrun usually means an exhaust leak somewhere - fresh air gets in and re-detonates the semi-burnt fuel. Check the elbow on the collector box and/or each of the headers