VFR 750 1995 with starting issues and rough idle. (New to biking)

Discussion in '3rd & 4th Generation 1990-1997' started by WillemK, Aug 5, 2015.

  1. WillemK

    WillemK New Member

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    Hello all,

    I'm from the Netherlands and just bought my first bike.

    I'm new to this forum. I've read a few posts when I decided to buy a Honda VFR 750. Now I own a 1995 750. It looks as if it's in great shape and has only done 40000 km (24000 miles). From the first meters I'm hooked. The deep growl when I open the throttle and the forgiving handling are great.

    There are however some problems. It has issues starting and runs rough when idle.
    In the manual it states that I have to set the choke fully on before starting. If I do so, it won't start. I have to crank it many times, set the choke half open and apply some throttle untill it gets going. When it runs, it runs. Starting with a warm engine is no problem. I've done about 400 kilometers in almost a week. When the engine is warm it won't stall, but the rough idle won't go away. At higher rpm's it runs and sounds good. It pulls cleanly in my opinion, but I'm not used V4 engines. It vibrates a bit around 4000 rpm, but that is something I also felt on my practise bike, an XJ6. After 5000rpm the power increases steadily.

    I've read that the most probable thing would be the carbs. Or could it also be the electric system?

    Thanks in advance,

    Willem.
     
  2. RVFR

    RVFR Member

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    Hmm, if you were state side I'd say run some chevron super through it for a few, well all the time. these bikes like premium fuel. Chevron has an additive in it that keeps injectors clean reducing valve carbon. it also keeps all those little vent and pilot jets clean, I've seen it in action so I know. But some here probably run what ever. LOL I try to only use the best is all I'm saying. but over were your at I haven't a clue what you have for fuel. but before you go getting into the enrichment system, I'd try run some carb cleaner through a tank or two. Mine when I had it, only took full choke when cold, once fired up and I mean like 4 seconds or less, I ran it at 1/2 choke for a couple minutes then off it went.
     
  3. karazy

    karazy New Member

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    You didn't state the rpm of the idle, so make sure it is around 1200 or more.

    I have always had to give a little touch of gas on cold starts, with full choke.

    Yes they have a slight shake below 5000rpm.

    You better get a pic up quick, before they release the hounds.
     
  4. WillemK

    WillemK New Member

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    The rpm at idle is around 1000. But it goes up and down.

    The fuel we use in the Netherlands has a minimum octane number of 95. If you go premium it is 98 or even more. The premium fuel has additives to keep your engine clean. I also threw in an engine cleaner. Still it isn't starting great. Maybe the carbs are to clogged with old fuel. The previous owner had it for over 16 years. So low mileage every year.

    I've called a motorshop, they'll take a look at it.
     
  5. WillemK

    WillemK New Member

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    honda-vfr-750-f-1169702.jpg

    And this is a quick pic, before the hounds are released.
     

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  6. squirrelman

    squirrelman Member

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    Changing sparkplugs is what i'd try first. :witless:
     
  7. Darth Vader

    Darth Vader New Member

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    Could be the carbs need synchronizing or cleaning. Don't think it's electrical.
    Nice looking bike
     
  8. 02 VFR Rider

    02 VFR Rider New Member

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    ck the rubber intake boots for dry rot and tears. sounds like vacum leak
     
  9. EpiEric

    EpiEric New Member

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    Yep. At first search for vacum leak; than change spark-plugs (iridium-ones on E-bay). Problem not solved ? Than clean/sync carbs....
    Don't think eather it's an electrical problem.....
     
  10. Badbilly

    Badbilly Official VFRWorld Troll Of The Year!

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    Why not do the plugs and carbs instead of guessing aboot a bike that is across one pond or another?

    The proprietary carb/injector cleaner may work if ya RTFM..Most call for adding the contents of the container to a full tank of gas in a cage.

    The old plugs may be fine and just need re-gapping and a little TLC. Could be the plugs are the wrong heat range.
     
  11. EpiEric

    EpiEric New Member

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    re-gapping doesn't solve the problem if te spark-plugs are too old.
     
  12. Jeff_Barrett

    Jeff_Barrett Member

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    Octane ratings in EU are slightly different (and appear higher) than that of NA. They use a different index.

    https://en.wikipedia.org/wiki/Octane_rating

    That said, I would take the carbs out and clean them well. Chances are, they are gunked up a bit. You can try running some Seafoam through a tank or two and to see if it helps without removing the carbs, but it's always best to just remove the carbs and do the job properly. Also, check your plug condition to ensure you are getting good spark and the air filter is clean and in good repair.

    RPM sounds a hair low, but then again, who knows what the jets look like in those carbs. :)

    If you're not comfortable doing the job, remove the carbs from the bike and take the entire unit to a shop to do the work for you. Put the carbs back in then the the whole bike back so they can sync them for you. :)
     
  13. Badbilly

    Badbilly Official VFRWorld Troll Of The Year!

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    It has not been established that the plugs are the problem. Plug condition and burn analysis had been around in one form or another for many years.

    So has the BS aboot plugs made of Unobtanium. Back in the day the Japanese guys would get pit passes and give oot Nippon-Denso plugs. We'd use them to warm up the bikes and then change to Champions or Lodge plugs when it was race time. Not quite everyone.. The Harley riders (as opposed to harleydoods) would not use the Japanese plugs.

    I have a BMW that takes a special plug or did until I found a Japanese version at aboot a fourth the price. The Champions could only be bought by the box (of 4) and were also used for lawnmowers..and I think a rare Triumph 350cc.

    1979 R100RS mit Krauser.
     
  14. WillemK

    WillemK New Member

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    Well, the carbs are synced now. If warm it runs about 1100 ~1200 rpm, still a bit nervous. But service is in a few weeks. Then the sparkplugs will be replaced and the complete bike thoroughly checked. Can't wait. :)

    About the spark plugs. Is regapping a method to determine the temperature of the spark?
     
  15. Badbilly

    Badbilly Official VFRWorld Troll Of The Year!

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    Re gapping in this sense means adjusting the gap to specification. The gap (distance) is related to heat range but not in a direct manner as in 2+2= 4. Either can be incorrect for your bike including just being worn oot.

    Honda has a free general mechanical guide that is a PDF. Also free is a factory manual (PDF) on your bike. Both documents are subdivided and indexed. If there is some part, system or procedure you are not familiar with, try Google or another search engine. Another source for basics is your public library's young peoples section.

    Ask a librarian, "I want to understand spark plugs." Works wonders.
     
  16. squirrelman

    squirrelman Member

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    Like BB sez, Willi, ya gots alot to learn !! :crazy:
     
  17. karazy

    karazy New Member

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    Take it easy on the newb, boys. He came here to learn, not get flamed, on his first day in school.

    How far was the sync off by? Did you get a copy of the numbers?
     
  18. WillemK

    WillemK New Member

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    Don't know Karazy, didn't got the numbers. But I'll bring the bike to the shop again very soon. I've driven over 700km's since I bought it, I love it and I think it is time to give the bike a new life. I'm going to stick with it and check it till every nut and bolt is OK. It'll be my learning bike. The things I learned so far, are where to look for damage if I buy a used bike, as mentioned in my other thread.
     
  19. EpiEric

    EpiEric New Member

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    That's the spirit ! Learning by asking and doing it yourself .....
     
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