Drag racing

so i took the 07 vfr800 to the track last friday and will be again this friday, to run some 1/4 miles. i got a best time of 11.9 at 120. the thing is i can not for the life of me launch with a rpm above 3000 with out the clutch turning into an on/off switch. i dont know whats going on with this bike, if its just a characteristic of the hydraulic clutch or theres some thing else going on. the clutch works fine for normal driving, but when i rev the bike up, the clutch has no modulation. i would really like to be able to launch in vtec...

please help guys


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Mine does the same thing.

so how can we fix this?
ive tried bleeding out the line. and cleaning out the chain gunk around the slave cylinder.
ive heard so many bs reasons about whats going on. last i heard is the clutch has to be bleed with the slave cylinder fully compressed...
worth a try???

or that the pushrod that goes from the slave cylinder to the clutch, develops a ring around it from wear and this needs to be polished out...

Hardly anyone here takes their Viffer to the strip so I don't know how much help you'll get.. My 4g VFR has a nice slip to the clutch, even when I tach it up and launch HARDWhat RPM do you try to launch when it gives you this problem, I know you said over 3, but how high over 3k?

i can usually leave at 3 grand maybe 3.5 thousand at the highest, before i have problems.
if i stage, pull in the clutch, rev to 4000 rpms or higher, i shit you not,
i could let the clutch out as slow as the hour hand of a clock and it will literally dump the clutch, when i get half way out.

i would say at 4 grand or higher there is absolutely zero modulation on the clutch.
at 4 grand or higher it is just the same as side stepping, no matter how slow and smooth you make your hand.
i hate it, i have felt that i was always very good with launching other cars bikes and trucks etc, but this bike makes me either look
like and idiot or a grandpa, everytime i leave the line.

with the mods ive done and how high im trapping, i should be getting close to 10s, instead im leaving the line like a grandpa, and lucky to break into the 11's...

so today im gonna change the oil and polish out that push rod, and install it in backwards(it is completely uniform and reversable)
i feel like maybe if i can polish out any grooves that maybe hanging up, and if not fully get rid of them at least put them in a different spot, this may cure it.

i really want to post up some vtec launch vids and low 11 high 10 time slips for you guys :D

Sounds good to me, but I'm not sure that listening to the growl for almost a second less would be a good thing.  Sounds great!

[image: View Post]VFRwhisp, on 02 February 2012 - 10:25 AM, said:

Sounds good to me, but I'm not sure that listening to the growl for almost a second less would be a good thing.  Sounds great!

lol i had to think about that one...

okay today i changed the oil, and pulled out the slave cylinder pushrod. i sanded out all the groves and polished it up. upon test ride, absolutely nothing has changed. i talked to a mechanic today and he said he thinks the discs are either damaged or warped. this is kinda weird, being that i bought the bike almost new(8000 miles in 09) and i now have 27000 miles, and its been the same the whole way through...

honestly i dont know if i should buy a new clutch, or not. my 750 night hawk had an awesome clutch. i could launch that bike at high revs all day. then i put in a barnett kevlar clutch and it turned to shit(actually it felt exactly how this one feels now)

bump

on a side note i went out on friday night.
ran a best of 11.7 at 119.6
not too shaby

Try a Barnett Kevlar clutch with some stiffer springs?

That, and check your clutch basket for notching.

Upgrade to a Brembo radial master cylinder with the same I.D.?

Other than that, I got nothing.

Launching in VTEC would be a wonderful thing :tour: I would thing that you might need wheelie bars though...
I raced my VFR one day last fall and ran a best of 11.95 at 114 uncorrected.

i guess next step is pulling out the clutch and inspecting it

I've done some practice launches at a few track days between 10-11k rpm. Mine is the same way. I just barely move the lever to slip the clutch. From full slip to full grab is maybe 1/4". It seems once it is rolling and has a load you get a bit more play, but it isn't much.

I've done some practice launches at a few track days between 10-11k rpm. Mine is the same way. I just barely move the lever to slip the clutch. From full slip to full grab is maybe 1/4". It seems once it is rolling and has a load you get a bit more play, but it isn't much.

Thats a good point. My method is to hold at desired RPM (about 7-8k) and then as soon as I start slipping the clutch I twist it to full throttle and mine slips nice.

Can't wait to get some passes in this spring. I'm planning on upgrading springs and plates sometime soon.
Edited by NakedViffer, 06 February 2012 - 12:50 AM.

This exact thing happened to me a couple of years ago. It was right after a track day, where I'd done my share of shaming riders on flashier/faster bikes, and I was feeling pretty smug. I was waiting at the lights in my flashy one piece leathers. The lights turned green and I decided to leave a bit dramatically. I dialed around 5000 rpm on the tach and let out the clutch carefully... only to experience the clutch engage fully and jerking the front wheel rather disgracefully. I disengaged the clutch and let it out again, trying to be more careful only to experience the same. This happened about 4 times when I finally understood the clutch wasn't going to engage smoothly. My smugness disappeared real quick, I tell you, here was a first-class schmuck, with full leathers no less, who was barely able to get his bike going from a stop.
When I got home, I started thinking about the incident. I had done a lot of agressive downshifts on that trackday, so it was possible that I damaged the clutch somehow. I had them changed a couple of weeks later. The old clutch plates looked fine actually, but there was a shiny spot on one of them, which I thought might have been caused during the trackday. I have done some high rpm launches after that and all seemed to be fine. Right now I have the Torocharger installed (the kit comes with stiffer clutch springs) but I have some issues I need to clear before making high-ish rpm launches and clutch modulation may be the least of my worries then :-) ...

I've done some practice launches at a few track days between 10-11k rpm. Mine is the same way. I just barely move the lever to slip the clutch. From full slip to full grab is maybe 1/4". It seems once it is rolling and has a load you get a bit more play, but it isn't much.

definitely true. so whats your procedure on launching at 11000? like how do you it, step by step?
im beginning to think its less somethings broke, and more i just need to work on technique on this bike.

I've done some practice launches at a few track days between 10-11k rpm. Mine is the same way. I just barely move the lever to slip the clutch. From full slip to full grab is maybe 1/4". It seems once it is rolling and has a load you get a bit more play, but it isn't much.

Thats a good point. My method is to hold at desired RPM (about 7-8k) and then as soon as I start slipping the clutch I twist it to full throttle and mine slips nice.

Can't wait to get some passes in this spring. I'm planning on upgrading springs and plates sometime soon.

wow thats crazy, id like to do that, but i dont have the balls. i feel like id just flip or spin up the back...
can you elaborate on this some more, and what its like?

This exact thing happened to me a couple of years ago. It was right after a track day, where I'd done my share of shaming riders on flashier/faster bikes, and I was feeling pretty smug. I was waiting at the lights in my flashy one piece leathers. The lights turned green and I decided to leave a bit dramatically. I dialed around 5000 rpm on the tach and let out the clutch carefully... only to experience the clutch engage fully and jerking the front wheel rather disgracefully. I disengaged the clutch and let it out again, trying to be more careful only to experience the same. This happened about 4 times when I finally understood the clutch wasn't going to engage smoothly. My smugness disappeared real quick, I tell you, here was a first-class schmuck, with full leathers no less, who was barely able to get his bike going from a stop.
When I got home, I started thinking about the incident. I had done a lot of agressive downshifts on that trackday, so it was possible that I damaged the clutch somehow. I had them changed a couple of weeks later. The old clutch plates looked fine actually, but there was a shiny spot on one of them, which I thought might have been caused during the trackday. I have done some high rpm launches after that and all seemed to be fine. Right now I have the Torocharger installed (the kit comes with stiffer clutch springs) but I have some issues I need to clear before making high-ish rpm launches and clutch modulation may be the least of my worries then :-) ...

hmmmmmmm so you had the same problem as me, then replaced the plates (friction and metal? stock or aftermarket? springs?) and it went away completely, and now youre able to do high rpm launches? im feeling tempted... lol

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I bought aftermarket clutch plates from EBC but I can not remember the details :blush: , I'll look it up though. I remember looking for Kevlar but there are none for VFRs. And another thing. When I say high rpms, it's not like what you're doing at the track, I used 5-6K tops, which I couldn't modulate before and I could after the clutch swap. As soon as I fix the throttle response problems with my bike, I'll see how the clutch behaves and post it here...

[image: View Post]arrow, on 07 February 2012 - 04:50 AM, said:

I bought aftermarket clutch plates from EBC but I can not remember the details :blush: , I'll look it up though. I remember looking for Kevlar but there are none for VFRs. And another thing. When I say high rpms, it's not like what you're doing at the track, I used 5-6K tops, which I couldn't modulate before and I could after the clutch swap. As soon as I fix the throttle response problems with my bike, I'll see how the clutch behaves and post it here...

Cool  - if you have the Torocharger - yes def post up when you run! ---  Curious as to times on the boost...

plus 1!!!!!

Okay guys problem solved. Basically the teeth on the friction plates have become razor sharp over time. Yesterday I pulled the clutch apart inspected everything, and spent a solid 10 hours sanding out all the sharp edges on the steel plates and friction plate's teeth that slide back in forth in the inner and outer clutch housings. It appeared the housings themselves had a little wear as well, but not significant. I am going to go ahead and polish those out as well during the next oil change. Next time i will be doing this with a dremel and proper attachment. I might go ahead and start with a fresh set of oem friction plates.

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Here it is, finally able to feather clutch in vtec!!!!
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On a side note as of last Friday I have gotten my 1/4 mile times down to 11.457 @ 119.55 mph. (still launching at 2-3 thousand rpms).
Also in regards to the Barnett clutch springs, I haven't noticed shit. They were a little bigger and prettier, but that's about it. No added clutch lever pressure or anything.
I am not sure if swapping out the clutch springs had any effect, what so ever....

^^^^ - 11.4s ---  That's pretty good. The pro moto rag guys are running 11.1s, - 11.3s.........

-- I'm still aching for somebody with a torocharger to crank off some quarters and tell us how it goes!