chrisf
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 posted on 10/4/06 at 03:37 PM |
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Two Questions--Help
Hi guys:
This is actually a two question post…
First (and I know we discussed this before, but I want to be certain), I’m still having an issue with the shifting. From a standstill, when I shift
into first, there is a very loud bang and the car jumps slightly forward. It truly sounds like something in the drivetrain is about to snap. I have
the clutch all the way in, and the car does not stall, but it is very concerning just the same. I made a
video of it, but it does not really show how dramatic this really is. Will you guys
take a look at the video and tell me if it is normal?
Second, when driving, I hit a very loud flat area around 2.5k RPMs. What happens is that I’m pulling very smoothly, then I get popping in the carbs, a
stutter, then I take back off again. When I had the bonnet off, I saw a small smoke plume come from the carbs. What’s up with this? Do my carbs need
some tuning? This doesn’t seem very bike-like.
I updated my webpage with a video of me driving around. It’s the first video on the page (sorry it’s so dark), and you can see/hear the carb popping
issue occur around the 1 minute mark.
Finally, I posted some pictures of my build thus far. It is not quite as smooth and polished as the kits you guys get, but I’m quite proud of it
because it’s my first build. The pictures are of the final mockup of the fiberglass panels, before I paint the car, rollbar, etc. later this week.
--Chris
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JoelP
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| posted on 10/4/06 at 03:42 PM |
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the flat spot could be it running a little lean due to the less restrictive air filters and exhaust (i assume they are less restrictive anyway!). You
would usually expect to rejet a bike engine when it goes into a new environment. My friend tells me they usually end up lean, and can melt a piston if
abused too much before sorting it! Worth doing.
The bang is loud, but it does sound very similar to mine. Try holding the clutch completely to the floor for 5 seconds before selecting first, see if
it changes. Mine wouldnt do it if i paused.  In fact, i do it fast to make it bang so that i am sure its in gear!
I strongly suspect your clutch is dragging a little, just enough to make the box spin when its in neutral, hence the louder noise and the more
pronounced jump forwards, before the weight of the car takes over and forces the clutch to give in.
[Edited on 10/4/06 by JoelP]
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hector
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| posted on 10/4/06 at 03:45 PM |
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the clunck you are getting is very normal for bike engines/g boxes-nearly all bikes do it but to varying degrees.
As to the popping etc, has it been suitabally rejetted to your air intake/exhaust?? Past experience with big bikes is some bikes run like a bag of poo
if you remove or drill airboxes without rejetting! I assume your valve clearances are all ok
NOt saying it is that but worth checking
cheers
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chrisf
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| posted on 10/4/06 at 04:23 PM |
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Hi:
Thanks for the quick replies. OK, so the banging is OK. It’s weird that it is as violent as it is and nothing breaks. I’ll try adjusting the cable a
bit to make sure the clutch arm is fully moving.
Regarding the popping, it is a small world. I bought my engine off an English guy whose company transferred him to the states. The engine came from a
Westfield and was replaced by a Busa engine. The previous owner had the engine dyno tuned by
TTS. That said, the second cylinder (#3 I think) from the front is blueing the exhaust. I’ve also had the carbs apart for cleaning more times
than I can count. Is it possible the carbs just need to be balanced? I think I fiddled with the balancing screw before I knew what I was doing.
--Chris
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smart51
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| posted on 10/4/06 at 05:47 PM |
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Was the engine tuned for the air filter and exhaust that you have? If not, then it will need doing again.
You could try richening up the idle mixture screws. This should affect the low rev (upto 3000) performance of your engine.
You could also try moving the circlips on the jet needles one groove towards the pointy tip. If one or both of these reduce the problem then
you'll need to get it dyno tuned again.
One exhaust header is bluing? It sounds like that cylinder is getting hotter than the others. Check that the carb setting are similar between
cylinders and that the carbs are balanced.
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Hellfire
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| posted on 10/4/06 at 05:52 PM |
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The knock you hear when engaging first gear is normal with a standard transmission. It is less noticable when in the higher gears. You can buy a
Torque Resiliant Tube which reduces/eliminates this knock - we had our's recently done by:
Dunning & Fairbank Ltd, Tel:01132488788 Fax:01132489619 Mb:07720471124 www:propshafts.co.uk Contact: Andrew Dunning
The coughing and spluttering is from a badly tuned engine... get it tuned properly. We used Holeshot Racing in Bradford... Jack Frost 01274 722200 or
email: info@holeshotracing.co.uk or http://www.holeshotracing.co.uk
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kb58
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| posted on 10/4/06 at 07:53 PM |
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Except he's in the US!
About the banging noise, you said the car jumps forward a bit. That's not right since it means somehow turning force is getting through the
transmission even with your clutch in. My guess is the clutch is not fully disengaging.
About the engine, get it tuned before the engine gets hurt. Either the second cylinder is too hot or the others too cold and it's probably
best/easiest to have it tuned, I'd assume by a bike shop.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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