CBR250RR clutch when wheelieing

[matoc]

Hello KiwiBiker!

I've been a member for a few months now, but have never really had anything of worth to contribute so this will be my first post!

I own a CBR250RR and I'm loving it. I started on a little RGV150 but got bored rather quickly and asked the bank very nicely if they'd buy me a new bike. Anyway, I've been on the CBR for a few months now and first tried to wheelie it a couple weeks ago, and just to clarify, this is not a "teach me to wheelie" thread. I'm able to easily get the RGV up and have had some practice off road on a DRZ250 and DRZ400, both of which I can mono. This is more to do with the CBR's clutch and whether you think it needs to be looked at.

I'll try my best to describe the situation.

1st gear, I take it to about 20km/h, I slip the clutch and roll on the throttle. This is enough to get any of those other bikes on one wheel. The problem is that the clutch is not engaging instantly once I release it, and therefore providing the kick required to wheelie. Instead it slowly engages, dropping the revs slightly and once fully engaged they build as usual. The bike then accelerates just as quick as it usually would, keeping the front end down. It feels like there is an auto-clutch increasing the time it takes to engage when in the high rev range.

I have spent quite a bit of time experimenting with this, such as reducing the amount I pull the clutch in; reducing revs (as low as 10k); increasing revs (up to near redline); trying in 2nd gear; putting one foot on the pillion peg; and even going spider-man and sitting on the pillion seat. I assume it's not a problem with the engine because if I leave the clutch out of it and try snapping the throttle off and then on in 1st the front gets very light and just about bounces.

A friend of mine, Hamish Murphy, has also had a few attempts. He used to own a Hyosung GT250R that he could wheelie, which is pretty similar to the weight distribution of the CBR. The fact that it's a twin could make a difference, but not in the way the clutch engages so I highly doubt it's that. I'm sure he'll be around soon to share his thoughts.

The bike has done just over 50,000 km so my guess is that it is simply a worn clutch, something I will have checked when I have the money to take her in for a service. However I thought I'd post this to see what the rest of you think, so if anyone here has had similar problems please let me know!

And before any of you get shitty... I do all my wheelie practice on a very quiet street that lies between two fields, so I'm not pissing anyone off with the 19,000 rpm scream of my baby blade. I wear all the right gear, avoid any cars that do happen to pass me, and yes I know it is a little hard on a 250cc!

Thanks in advance!

[samgab]

I'm no mechanic, but it sounds like a slipping clutch to me. I don't think it's a design feature.

[racefactory]

Dude have you adjusted your clutch properly? If there is little/no freeplay the clutch will not provide full engaging power...

Try give it a good 1.5cm of play at the bar end.

Have you tried launching the bike? Is it possible to get a good strong launch? Or same thing?

[Brett]

Yarp, clutch either needs adjusting or replacing. It will be slipping. They CAN wheelie.

[wbks]

Albeit for 10 meters!

[samgab]

Albeit for 10 meters!

Yeah, they're wheelie monstarrs!
Check out the huge wheelie on a CBR250RR here:
http://www.youtube.com/watch?v=gtpq7JtjEPs

Wow!

[The Pastor]

yeah i can wheelie my mc22. maybe replace the clutch?

[hmurphy]

The bike easily has the power, the throttle reacts instantly when snapped to pin position and it should easily wheelie with clutch. But the clutch disengage is soooo slow. No matter how I tried to slip it, and Matt, it just would not immediately dump the revs on the rear wheel. It would only very slowly let the revs be released on the rear wheel. Not even a slight pop up of the front wheel

[racefactory]

well I don't know about that cause I've seen a MC22 wheelie clutch wheelie dead easilly... so it's definately able.

[vtec]

I'd advise against clutching them up, you could damage your clutch. But hey, if you can do it fair play to you. I could wheelie my 12hp NXR 125, the CBR is harder to wheelie, it's front heavy, no torque, and has a sportsbike position. You need to thrash the clutch. Your problems are as others have suggested. Either needs adjusting or replacing.

[Dargor]

Does clutch ever slip any other time. Like if take off at warp factor 9 and stay in first gear till 17k rpm.

[matoc]

Does clutch ever slip any other time. Like if take off at warp factor 9 and stay in first gear till 17k rpm.

No, I've never had a slip once she got rolling and the clutch fully engaged. On the occasional balls-to-the-wall red light take-off it just does what I've already described, as in if I'm revving enough to make the front wheel normally jump slightly when I release the clutch it will just slowly engage, keeping the front planted but still giving me the great acceleration.

It seems to be slipping only if the revs would normally result in the front lifting, which wouldn't happen when simply accelerating on a 250 above 1st gear. So it does seem to be a worn clutch, giving enough resistance to stay engaged once fully locked but not able to instantly connect under the extreme conditions required to lift the front end until the wheel speeds up a bit and closes the gap between wheel revs and engine revs. Which would mean I'm just grinding it down further whenever I attempt a wheelie. No more of that I guess!

Not too much of a big deal since it's not impacting on normal riding, but it definitely will need to be looked at/replaced soon. Don't want it to worsen and, as you say, start slipping under heavy acceleration, something which could definitely happen if I scrape together the funds to attend the January 17th track day!

Thanks for the swift replies, stay safe!

[HDTboy]

Clutch is slipping. It's easy enough to fix. If you bring me a set of fibres, and the engine oil of your choice, I can do it for $60

[matoc]

Clutch is slipping. It's easy enough to fix. If you bring me a set of fibres, and the engine oil of your choice, I can do it for $60

That sounds perfect, except for the fact that you're in Auckland! I may hit you up if I head to the Iron Maiden concert in February. Thanks for the offer!