Problems with starting engine after installing clipons
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Problems with starting engine after installing clipons

This is a discussion on Problems with starting engine after installing clipons within the Technical forums, part of the Caferacer.net Forums category; Hi! I'm new here, so let me briefly introduce myself. I'm Mattijs, 25 years old, from Belgium. A few weeks ago I bought a fully ...

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  1. #1
    Junior Member Mattijs's Avatar
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    Problems with starting engine after installing clipons

    Hi!

    I'm new here, so let me briefly introduce myself. I'm Mattijs, 25 years old, from Belgium. A few weeks ago I bought a fully functioning, modified twin cilinder Suzuki GSX400e from 1985. The bike runs great, looks great and I unfortunately cannot ride it yet because I'm waiting for my riding lessons & exam to start in December.

    Now, the only minor thing I wanted to adjust was the front of the bike. The previous owner had an M-type handlebar installed together with the original and fully functioning head display (tacho, speedo and even a display that showed the gear you're in). Really nice as all of it was functioning well, but I really wanted the clip-on and minimalistic speedo look on the front. I'll give out a step-by-step explanation on how I got to work.

    1. I removed clutch lever, front brake lever, switches and all that together, then removed the M-handlebar.
    2a. Then I unscrewed the head display as a whole and disconnected the electronics from the main wires by simply unplugging it at the 'socket' (don't know the excact English terminology here).
    2b. As said before there is also a display that shows the gear you're in. The wires belonging to each of the 6 lamps inside the display run along the frame to the engine (I guess), beneath the fuel tank. Therefore, to disconnect these wires from their socket I had to remove the fuel tank to unplug it, as this socket was right underneath the tank and I could not reach it otherwise. As I also had to remove the fuel arms that lead to the carbs this might be the origin of all problems but I'll continue with my next steps.
    3. I removed the top triple tree and installed the new clip on handlebars together.
    4. re-installed the triple tree and all switches, levers etc in the reverse order in which I took it apart, together with new grips.

    Final result:
    Name:  20171030_214733.jpg
Views: 101
Size:  2.10 MB

    Now, after all was set (except for the speedometer), I tried to start the bike. First, nothing, when normally the bike would instantly start regardless of choke etc. So I made sure the fuel faucet was ofcourse opened, choke was opened but this did not help. I then decided to lift the fuel cap to make sure there was no vacuum or anything and huray, the engine kicked in! HOWEVER: it acted weirdly. The engine would rev up and down as if someone was yanking the throttle. Really rithmycal for about 7 times, and the the engine would start to rev up to the point I decided to kill it by turning the key. I tried this about 3 times and got the same story every time: some automated reving and then the engine would rev up to the point I had to kill it. I twisted the throttle at all stages of this event but it did not seem to have an influence on anythig. I'm sure that all is reinstalled properly though: throttle springs back nicely and I made sure the cable actually moves the wire down between the two carburetors. Also clutch feels the same, and seems to work.

    As it was late I went to take a shower and wanted to wait for the next day to worry further. However, after I got out I decided to try once more. So I again wanted to start the engine, but now it does not start at all anymore. Sometimes it slightly seems as if it wants to kick in action, but it doesn't. Not with the fuel cap removed or choke opened or anything.

    I hope this rather detailed explanation can be of any help for you guys to help me out! It seems to me like a fuel-related issue. I did not touch anything besides head display electronics, clutch and gas cable and ofcourse the fuel arms...

    I would like to state that I am however not an experienced mechanic at all. I did have some oldtimer 50cc one cilinder mopeds back when I was 16 and tried to learn some stuff of it, but that's a while ago and I must admit that all I learned was done throuh internet and fora, so I'm not to self assured of my own skills!

    Thanks a lot in advance for reading this book and hopefully there's some people that can help!
    Regards,
    Mattijs

  2. #2
    Senior Member hillsy's Avatar
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    You've probably connected the fuel lines incorrectly when you took the tank off - it sounds like it's run out of fuel (lean) which would explain the manic revving....and then nothing. Check the carb bowls are getting fuel.

  3. #3
    Senior Member BigAl8295's Avatar
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    Quote Originally Posted by hillsy View Post
    You've probably connected the fuel lines incorrectly when you took the tank off - it sounds like it's run out of fuel (lean) which would explain the manic revving....and then nothing. Check the carb bowls are getting fuel.
    I'd also re-check the routing of your throttle cable.
    I like my shocks like I like my carryout. Cheap and Chinese.

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  5. #4
    Senior Member TrialsRider's Avatar
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    Your bike is equipped with CV (Constant Velocity) carburetors. The throttle cable opens a butterfly valve that allows the engine to produce more vacuum and the resulting increase in vacuum pressure allows a vacuum circuit to open the secondary valves which are slide valves. I think you have an improperly routed throttle cable that is causing one (or both) butterfly valves to open more then it should. Check your vacuum hoses in addition to the cables. The engine speed fluctuating up and down is typical for an uncontrolled vacuum operated throttle problem.
    I think I see a choke lever on your left handlebar, carefully inspect that also; the choke is a separate fuel circuit inside the carburetor. CV carburetors can have as many as 5 different fuel circuits in order to make the engine operate as lean as possible under all operating conditions and thereby comply with pollution emissions law.

  6. #5
    Junior Member Mattijs's Avatar
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    Allright thanks a lot guys! I got it working again.

    The problem indeed was to be found at the throttle cable: when re-installing it, I must have tightened the cable too much, causing the butterfly valve to be opened almost half when the throttle position was at 0. So I reinstalled and gave the cable some slack. Started at first ignition, same as before.
    Choke also still works by the way.

    However, I gave the bike some revs and when having the throttle about 3/4 open it seemed as if the bike was about to stall. When releasing, it idled again but very slowly. Eventually it died when idling, but it fired up back again when I tried again.

    Is this something that I should worry about still? Or is this maybe because there was not enough fuel yet in the system or something?

    Thanks again for your help!

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