krusty Posted March 4, 2010 Share Posted March 4, 2010 I have just collected an '82 XS400 SE 4G5(UK spec), It was bought as a non runner, but after delving into the bike a little bit, it seems it has the BS32 carbs from an XS250, has anyone used these carbs succesfuly with this engine and if so could they recommend some jet sizes. It appears the carbs have standard XS250 jets and the only change I have found from standard is that the needle has been raised to the 4th notch(2nd notch is standard for XS250). I can't wait to get the bike up and running, as it's in generaly very nice condition and I'm sure will be fun to ride. I'll try and get some pics up when it's back in one piece. Cheers... Krusty. Link to comment Share on other sites More sharing options...
pepperami Posted March 4, 2010 Share Posted March 4, 2010 sorry i cant help you on that one, but i would love to know what you do find out so i will be keeping an eye this thread... i have a spare set of XS250 carbs so it might be useful if i get stuck.. be patient as there are a few wise old cookies on this forum, especially when it comes to XS400`s Link to comment Share on other sites More sharing options...
Paulwhite Posted March 4, 2010 Share Posted March 4, 2010 I have just collected an '82 XS400 SE 4G5(UK spec), It was bought as a non runner, but after delving into the bike a little bit, it seems it has the BS32 carbs from an XS250, has anyone used these carbs succesfuly with this engine and if so could they recommend some jet sizes. It appears the carbs have standard XS250 jets and the only change I have found from standard is that the needle has been raised to the 4th notch(2nd notch is standard for XS250). I can't wait to get the bike up and running, as it's in generaly very nice condition and I'm sure will be fun to ride. I'll try and get some pics up when it's back in one piece. Cheers... Krusty. cant you go to a dealer and see if they know? i know most have records on jet sizes if not you can either wait for a reply or if it was me hav a play with some larger jets. Link to comment Share on other sites More sharing options...
krusty Posted March 4, 2010 Author Share Posted March 4, 2010 I have never played about with jetting, so I wouldn't know where to start. I figure trying standard 400 size jets might be a starting point but I don't want go spending money on jets that won't work properly, I really need a starting point to work from, I'm guessing that running the carbs with standard 250 jets will give lean running, but again I don't know for sure. I can see that the 250 carbs wil not give me full power but for normal loads and general pottering about I'm hoping they will work ok. Really need some old school know how on this one... Krusty. And my local Yam dealers are not interested in talking to the likes of me with my old bike, 'cos it's not making them a tonne of cash. So thats not really an option I'm afraid. Link to comment Share on other sites More sharing options...
sdhynds Posted March 5, 2010 Share Posted March 5, 2010 I have never played about with jetting, so I wouldn't know where to start. I figure trying standard 400 size jets might be a starting point but I don't want go spending money on jets that won't work properly, I really need a starting point to work from, I'm guessing that running the carbs with standard 250 jets will give lean running, but again I don't know for sure. I can see that the 250 carbs wil not give me full power but for normal loads and general pottering about I'm hoping they will work ok. Really need some old school know how on this one... Krusty. And my local Yam dealers are not interested in talking to the likes of me with my old bike, 'cos it's not making them a tonne of cash. So thats not really an option I'm afraid. I have an 82 xs400 maxim and am in the middle of converting to pod filters and re-jetting, but am by no means an expert. Here is what I know so far and maybe it will be of assistance. The manual that I have indicates the jet sizes are 127.5 for the left hand and 117.5 for the right hand. My bike had 125 and 115's in it. You can find them very cheap ebay and so I have got bigger ones to play around with. I will see how it affects the mixture with the new air filters. I started a thread a week or 2 ago and another guy said he was running 130's but was thinking about going bigger yet. I am waiting on filters to ship but will have more details in a week or so. Hope this gives you somewhere to start. Link to comment Share on other sites More sharing options...
1984maxim400 Posted March 7, 2010 Share Posted March 7, 2010 My bike to is 125 and 115's and new air filters you said some guy is running 130's is that in the left and right. and i got a 1982 maxim 400 to. the carbs on it is mikuni kogyo. are your carbs a bs34 or kogyo. and where did you get your biger jets at. thank you. Link to comment Share on other sites More sharing options...
adioskater6888 Posted March 13, 2010 Share Posted March 13, 2010 mikesxs.net has jets for the bs 34 and 38 they're 6$ and they come in a pair i just bought some for my bike Link to comment Share on other sites More sharing options...
kmac Posted March 13, 2010 Share Posted March 13, 2010 If mikesxs.com is out of the sizes you want to try, you can also find main and pilot jets on denniskirk.com. They have them for the same price. I ordered Monday and they arrived today. They had the ones in stock that mikesxs was out of. I added a mac 2 into 1 exhaust going through the tuning process too. Link to comment Share on other sites More sharing options...
krusty Posted April 30, 2010 Author Share Posted April 30, 2010 Time for a little update, I have had a play with my carbs and the following steps have been taken so far: firstly I set the carbs to standard 250 specs and tried a couple of runs, general low speed running was ok, the biggest problems were lack of midrange, real bad vibes over 4k revs, a hot stalling problem when at idle and popping thru the exhaust when throttling off. I then tried adjusting the pilot air screws and found I have lost all but a small amount of exhaust pop and the idle is much smoother(screws set at 4 turns out), then I raised the needles to the 4th notch, this leaves one more if I need it, and this has improved the overall running, reduced vibes and exceleration is stronger. The hot stalling is still evident and when getting into full throttle the main jets are struggling to keep up, theres a big flat spot. My next move has been to order up some jets, I have order two sets of pilot jets and two sets of mains. Pilot: current size 17.5, ordered 35 and 40 two of each Main: curent size is 110, ordered 117.5 and 122.5 two of each The pilot jets seem a little on the large size but they are actually quite a few steps down on standard 400 sizes and some further adjustment of the pilot circuit should make them work, I'm hoping these will help the hot stalling issue. The mains are even further down on stock 400 sizes in relation to the pilot jets due to the carbs smaller 32mm bore, I am really only looking for midrange flexability and not out right power so this would seam about right. When these turn up I will have a further play and report back. In the mean time please give me some feedback from personal experience on rejetting techniques, as stated previously I am still in the early stages with carb tuning and any advice would be greatly apreciated. One thing I would like to know is, Why do US spec bikes run different jet sizes on left and right cylinders??? All the UK specs are for same size jets left and right, Guessing it's something to do with the EGR circuit??? Link to comment Share on other sites More sharing options...
Recommended Posts