nobbie1517 Posted April 3, 2013 Share Posted April 3, 2013 A little help please I have 1979 dt175 with a giannelli front and tail pipe Does anyone know if there should be any carb changes (pilot, needle, main jets etc) Or any air box mods. Mine came with standard jets and needle position (main jet I think 140 my Haynes doesn’t quote a size) but the air box had been drilled with six 12mm(ish) holes. The trouble I have is in starting It will start with no choke but only after kicking it enough times to shatter yer kidneys And that’s even in the cold weather we are having now, any hint of choke and the engine just dies All jets and holes are clean the issue I have it tends to overflow petrol when on the side stand so I turn the petcock off all the time now If the level is too high up into the bowel and pilot jet after flooding will that make it difficult to start. I just don’t know I am now on a new float seat and needle, and the side stand has been straighten back to its original shape so the bike isn’t leaning at any stupid angle and the float heights checked time and time again. Just what am I doing wrong? It also tends to run a little rough at lower throttle settings and seems to even out at about ½ throttle opening Sorry but I don’t know if these are separate issues or all interlinked Link to comment Share on other sites More sharing options...
Moderator Cynic Posted April 4, 2013 Moderator Share Posted April 4, 2013 Shouldnt make much odds unless you live on the limiter. Maybe lift the needle a clip. It sounds like more of a float height issue. How are you checking it. Outside chance of crank seals or compression but float would be my first check. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 4, 2013 Moderator Share Posted April 4, 2013 seems that it is too rich causing difficuly in starting, first confirm this by taking out the air filter not sure whether cynic meant lift the need clip a notch there Link to comment Share on other sites More sharing options...
Moderator Cynic Posted April 4, 2013 Moderator Share Posted April 4, 2013 The gianeli pipe generally needs the little circlip on the needle placing one groove lower. Therby richening the mix. Doesent sound the issue here. .Airhead has a 79. Minevis a year later and breathes a lot easier..heh heh....(read quicker ahem) Link to comment Share on other sites More sharing options...
nobbie1517 Posted April 4, 2013 Author Share Posted April 4, 2013 I’m checking the height as per owner’s manual pictures Measuring from the gasket face top the top of the float whilst the tang is just touching the float valve (but not depressing it) There was a noticeable difference in the springiness between the little plunger on the old float jet (next to no resistance) and the new float jet (very stiff indeed) Don’t now how critical that is. I suppose it just acts like a little shock absorber Compression is good and seals are new so hopefully not leaking but I haven’t checked I will try without the air filter first for the starting issue and then look at the clip position for higher throttle opening Cynic re. Airhead has a 79. Minevis a year later and breathes a lot easier..heh heh....(read quicker ahem) What are the difference between the 79 and 80 models as far as engines go. Or shouldn’t I ask Thanks for the input Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 4, 2013 Moderator Share Posted April 4, 2013 I know about the stiffness of your new float valve compared to the old one nobby I've been going through the same scenario with mine. I have been experiencing overheating problems with mine and I'm counting on it that this is the cause...ie the stiff sprung valve is causing a lower fuel level and at high fuel demand is dropping the level and uncovering the pilot jet housing...to that end I have set a level 2mm difference ie@ 19mm instead of 21mm...all as yet untested because of the feeking weather weve had lately! (Bear in mind that the stated 21mm level has a +/- tolerance of 1.5mm anyway) The differences between mk1 and mk2 are ignition cdi's/stators and airboxe's and carburettors. Link to comment Share on other sites More sharing options...
blackhat250 Posted April 4, 2013 Share Posted April 4, 2013 Compression is good and seals are new Confirm this " has engine been stripped ? also what pilot jet is in it,,? also check air screw for turns out,,, Link to comment Share on other sites More sharing options...
nobbie1517 Posted April 4, 2013 Author Share Posted April 4, 2013 yes engine was totally stripped. all new seals and bearings.cylinder was in good shape. measured all the way down, but i put new piston and rings and small end in just cause it was down that far its got the standard pilot in 2.5 or 25 some thing like that sorry i cant remember , but the numbers matched what was in the haynes book when i checked the air scew- i followed the setup proceedure in mikuni pdf down load but some thing didnt tally with what it said i should see. i could turn the screw in to the point of stalling the engine but i could wind it almost all the way out past the point of where the bike seemed to run its best with little change to the sound of the engine but this may have been done with the fuel level too high. if that has any effect Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 4, 2013 Moderator Share Posted April 4, 2013 .............. but this may have been done with the fuel level too high. if that has any effect ?? what I was saying is the fuel level may be too low Link to comment Share on other sites More sharing options...
nobbie1517 Posted April 4, 2013 Author Share Posted April 4, 2013 yes airhead sorry you beat my reply i have been re reading the post. im a little rusty on carb setup now adays too many EFI bikes i think Link to comment Share on other sites More sharing options...
nobbie1517 Posted April 4, 2013 Author Share Posted April 4, 2013 what i should have said is that all my setting up was done with the weak float plunger allowing the level too high and the pilot mixture to be too rich for starting and slow running (but i dont know what difference a few mm of height would make)but as you say the tolerance is +/- 1.5mm anyway i now have the stiffer plunger in and even though the float height measures the same.the physical height applied by the petrol will be less if the level is lower in the pilot jet will that mean that my air screw settings will now be all wrong ( cos that was set to higher level allowed by the weak plunger) ah knackers what chance do you all stand .im confusing myself now Link to comment Share on other sites More sharing options...
Moderator Cynic Posted April 5, 2013 Moderator Share Posted April 5, 2013 When you did the seals you did remember the little o ring under the collar behind the primary drive gear. As to differences. Flat out there is not much in it but mine is far pepier if that is a word to use. I have wheel lifting punch in the lower gears at the expence of fuel economy. Top wack for me is about 70miles from a tank. If i enjoy myself that can easily drop to 40. Even worse off road. That may be a quirk though as i have the early ig with the later airbox. Gives the bike quite a personality. The best comparison i think is Gary Lineker and Vinny Jones. Both footballers, both from the same era but very different personalities. On mine traffic becomes targets of oppotunity. Anyho. Had the ol girl since i was 16. Becoming known as trigger funnily enough (not very many original parts). Link to comment Share on other sites More sharing options...
nobbie1517 Posted April 5, 2013 Author Share Posted April 5, 2013 ha. lineker and jones.....excelent i think my bike at the time beinging would be fred davis and steve davis, different eras, both snooker players, both not so interesting.....(a little unfair i like steve realy) yes i fitted a new o ring under the coller (even bought a spare at that price. just in case i nipped it but all went together smoothly but that was only after seeing it on this forum. cos i had missed it on the drawings when i was ordering all the new seals and bearings etc the crank double lip seals were fitted with the cases warm and the way round that ty trails website suggests for those seals i have had delivered a couple of new bowl gaskets ( the other new one! is a little tired now. so this afternoon i will remove the carb and try to see whats happening with the float height and needle Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 5, 2013 Moderator Share Posted April 5, 2013 It's hard to start so also check the spark...weak and yellow or fat and blue? Link to comment Share on other sites More sharing options...
nobbie1517 Posted April 5, 2013 Author Share Posted April 5, 2013 i checked plug and although nice and blue its not as fat as id have thought, the plug is a NGK Iridium BR8EIX with a tiny electrode so ive bought a couple of NGK B8ES in case i have to do a plug chop airhead- you mentioned yours was overheating. are you going off the plug colour or are you measuring cyclinder head temp i have have a k type thermocouple and display (havnt used it yet ) just to help with setting up but i cant find any info on what temps to expect do you have any ideas Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 5, 2013 Moderator Share Posted April 5, 2013 no not going off plug colour but actual temperature readings, I've seen that when revs are high on dual carriagway or motorway the temperature never seemed to stop increasing. I checked the crank seals OK put bigger and bigger jets in but never seemed to get a good plug colour or a stop to the ever increasing temperature, so I had to find an answer ...I have a float valve with a stiff spring (nothing wrong with that per se) but that...coupled with a float height more than 21mm made me think that perhaps the fuel level drops enough in these high revving situations to actually uncover the tube that the pilot jet sits in...that would allow air to be drawn in to the intake at that point in time and may be the cause of my overhating...other evidence was a slight 'hanging' of the revs when exiting the fast road/motorway...yeah quite posiible...it's quickly settled...well it would wouldnt it, as the carb fuel level rose again due to the reduced load well thats my theory, I really hope I'm on the right track with this because I'm out of ideas after this Oh another clue is that I have never been able to get a sensible plug colour lately It's always been a bit washed out and not a definite colour, any shade a brown would have been nice but Iv'e seen it brown (ish) but with a whitish on the opposite side even with big jets in high temperatures I have seen 230C after a short blast down the motorway, I actually saw 250C on a long dual carriagway trip during last years 2 stroke day from squires...not funny!!! Link to comment Share on other sites More sharing options...
nobbie1517 Posted April 5, 2013 Author Share Posted April 5, 2013 thanks for that i followed the link to the trailtech temp module. nice. its a little more compact than my K type on a copper ring plugged into a fluke meter strapped to the petrol tank i have been comparing my carb to one i ve just had delivered. advertised as a new mikuni £70 without the box. although the casting is good quality i fear it is a fakini ( no sh1t sherlock) but it does have a small tang on the floats that sits against one of the posts to restrict the distance the floats can drop drown mine doesnt. it looks like it may have had, so with carb bowl off and turned the right way up i can lower the floats enough that when you push them back it jams the float needle in the open position and i dont have the lower them too far. whether or not they would ever get to the postion in reality i dont know but im going to see if i can pop them into the mikuni, to sort the flooding. may be mine is intermitently jaming after a spell at high speed then freeing itself etc etc etc. thinking about i have on occations come to traffic lights and the idle has sat quite high and not settled back, but get to the next set and its ok i had tried to spray for leaks which made no difference, and it is a definate on/off type of fault if you know what i mean i,m sorry not to have any input on your problem, but as you can see i cant even sort my own out Link to comment Share on other sites More sharing options...
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