1641 with 34 pict 3, jet size

Discussion in 'Mech Tech' started by brothernumberone, May 10, 2019.

  1. Does anyone have any details for jet sizes for a 1641 running a standard carb.
    Only ever fitted 1641’s with twin carbs, but the owner wants to stay stock looking and no one has a recommended main jet size.
  2. Its 5% bigger capacity.

    If stock main is 125 then if fuel went through the hole nicely in proportion to jet area then increase of 5% area would correspond to a jet diameter increase of square root of 1.05 giving about 128. Hence lots of mention of people using 127.5... or maybe 130 but that will be 8% bigger area.

    In other words... not a lot of change needed..
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  3. You could stick with the stock 127.5 - a 1641’s barely any different to a 1600. Or go to a 130.
    brothernumberone likes this.
  4. When i looked at this i seem to remember it was a 130 ...

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  5. Thanks chaps. The carb came with a 130, so I stuck that in as a starting point. I wouldn’t have thought it necessary either, but Heritage got a bit clucky about correct jetting and warranties, but yet couldn’t offer any advice on sizes.:rolleyes:
  6. Go for it. I've run up a 1776 with a 130, and it was fine.
    brothernumberone likes this.
  7. I have a 1641 and run it with the standard carb and standard jets.......not that I know what size they are but I haven't changed them in the years I have owned it...
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  8. I had the same with them when I got a 1641, spoke to their technical people and that wouldn't offer anything solid to ensure warranty is ok. As I would have to rolling road it anyway I just get a pair of 34 ICT's and avoided the problem

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  9. Baysearcher

    Baysearcher [secret moderator]

    I bet they suddenly find an expert should you experience problems with the carb!
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  10. Ask them how many warranty claimes they pay out on. I personally will not use them.
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  11. I went through a stage of not using them, but realised all the big companies are basically the same, they all sell the same tat. I’ve not had an issue with returning stuff, but must admit i’ve never returned an engine. I use jk sometimes, but they get orders wrong more often and it’s a pain sending stuff back. Heritage are local, so i’ve gone back to using them mostly for convenience.
  12. What warrenty are we talking
    Surely you can't go wrong using basically standard jetting?
  13. Sorry, should have explained better, it’s a 1641 from heritage, one of there ‘all new parts’ one.
  14. They must be aware that folk could put anything on them. They can’t be too fussy, especially if they’re clueless about jetting.
    brothernumberone likes this.
  15. I hope so!
    snotty likes this.
  16. Be interesting to know what VWH’s “all new” engines are like. I thought they’d stopped doing them.
  17. The one I have had for 4 years has been spot on, no issues. I know @Ozziedog had a different experience though

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    snotty likes this.
  18. Heritage offered me an all new engine when I asked last year.
    They couldnt guarantee a delivery date within 10 weeks so I went to JK for one of theirs that turned up in 3 days.

    In fact Heritage phoned up a month later to check if I maybe needed an engine.

    All the warranty on mine says is invalidated if the 120 degC crank case temperature sticker changes colour. Its under the fan housing.

    So running a bit lean and pushing hard could do this. I cheated and reinstalled a full flow oil filter and cooler, I havent seen over 105 C since...

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