If you’ve got spark and compression is above 100 psi and fuel is getting through, the boots aren’t leaking (sucking air), the timing chain hasn’t skipped a tooth or something, then I would still go back to carbs. I would try another set of carbs. It’s easy for me to say though because I have so many extra sets. Graham
Sent from my iPad > On Sep 22, 2018, at 4:16 PM, Kevin Tsao <[email protected]> wrote: > > Hey Colin I tried the spark tester thing and got a pretty good spark up to at > least 20-25 kV for both coil systems by testing on all 4 igniter leads. I > also checked the resistance between the leads with the caps on and they were > both around 28 k ohms which is in spec according to the manual. I keep coming > back to compression. Won’t slightly low compression like 100 -125 psi cause > the engine to fire on starter fluid but not on regular fuel the same way weak > spark will? And Graham, the fuel has no rust, and when I checked the petcock, > the fuel strainer was very clean, no rust or debris. As for the carbs, right > now I don’t really see how there could be a problem with that, and I shot > carb cleaner through all the passageways I could see and they were clean. > Blew air through the jets including slow jets and could feel the air coming > out through the other end. For the slow jets I could see a tiny hole of light > looking through. And whether or not the carbs are okay, the engine will only > fire sporadically and not really run even with carbs removed and a good > spraying of starter fluid. > >> On Thu, Sep 13, 2018 at 6:13 PM Colin Evans <[email protected]> wrote: >> Hey Kevin, >> What got me focussed on the ignition system was this great article from an >> unknown author at Princeton. >> https://www.princeton.edu/ssp/tiger_cub/library/ignition_waveforms.pdf >> >> Check out page 4, which talks about mixture. Particularly paragraph 3 which >> talks about the volatage required to fire a rich vs. lean mixture. 3-4kV for >> 12:1 mixture, 7-9kV for a 15:1 mixture. Clearly plug gap, wire resistance >> and coil voltage have to be up to snuff to run reliably. This got me wanting >> to measure the firing voltage on my bike and it may explain why your engine >> starts on starter fluid but not on gas. That is, rich highly volatile >> mixture is easy to light. >> >> Colin >> >> >>> On Thu, Sep 13, 2018 at 5:18 PM Graham Rogers <[email protected]> >>> wrote: >>> When you say ‘not really any rust’ is there any rust at all. How about when >>> you stick your finger in there and rub the part you can reach? >>> >>>> On Thu, Sep 13, 2018 at 5:50 PM Kevin Tsao <[email protected]> wrote: >>>> Hey Colin, I’ll give that a try. Again, all 4 plugs had spark, they looked >>>> like a clean blue/white spark at least to me. I know the spark plugs also >>>> fired inside the cylinders because the starter fluid I sprayed in would >>>> pop and flame, albeit not steady or consistent enough to get the engine >>>> really running. And the tank looks pretty clean, not really any rust. >>>> >>>>> On Thu, Sep 13, 2018 at 1:13 PM Graham Rogers >>>>> <[email protected]> wrote: >>>>> Mmmm, good point Colin >>>>> >>>>>> On Thu, Sep 13, 2018 at 3:51 PM Colin Evans <[email protected]> wrote: >>>>>> Hi Kevin, >>>>>> I had a symptom very similar to what you are describing. I spent a lot >>>>>> of time checking carbs, fuel delivery, valve timing, ignition pickup etc >>>>>> but was getting nowhere. Eventually I went back to the plugs. Although I >>>>>> could see a spark I wanted a way to quantify it so I bought a spark >>>>>> tester like the one called >>>>>> “Thexton THE404 spark tester” on Amazon. About $11. It allows you to >>>>>> adjust the spark gap to see at what point the coils can no longer >>>>>> produce a high enough voltage to jump the gap. Very handy. >>>>>> >>>>>> Turns out I was doing my testing in my dim garage when I noticed with a >>>>>> wide gap there was a blue spark leaping out of the coils at the spot >>>>>> where they were injection molded. Closer inspection showed arcing had >>>>>> been going on for a while. I suspect the plastic get very hot and >>>>>> eventually fails over the years. >>>>>> >>>>>> Replacing the coils solved the problem completely. >>>>>> >>>>>> Worth a try for about $11. >>>>>> >>>>>> Good luck. >>>>>> Colin >>>>>> >>>>>> >>>>>> >>>>>>> On Thu, Sep 13, 2018 at 11:38 AM Graham Rogers >>>>>>> <[email protected]> wrote: >>>>>>> No need to separate them but if those low speed jets aren’t the right >>>>>>> size, either gummed up or reamed out too much, they can cause trouble. >>>>>>> Any rust in the tank? >>>>>>> >>>>>>>> On Thu, Sep 13, 2018 at 2:29 PM Kevin Tsao <[email protected]> wrote: >>>>>>>> Hmm okay, I’ll take another look at the carbs and jets. I’ll mention >>>>>>>> that when I cleaned the carbs I didn’t separate them, only removed and >>>>>>>> cleaned the float and vacuum bowls as well as the jets, floats, and >>>>>>>> piston/needles. Thanks everyone for the input though. >>>>>>>> >>>>>>>>> On Thu, Sep 13, 2018 at 11:20 AM Kyle Munz <[email protected]> wrote: >>>>>>>>> My compression has measured that low and my bike still runs. It can >>>>>>>>> be a bit of a bear to get going sometimes when it's cold though. You >>>>>>>>> mention needing choke and higher RPMs to keep it running. It may be >>>>>>>>> worth taking another look at the low speed jets. >>>>>>>>> >>>>>>>>> -Kyle >>>>>>>>> >>>>>>>>> >>>>>>>>>> On Thu, Sep 13, 2018 at 12:45 PM Kevin Tsao <[email protected]> wrote: >>>>>>>>>> Well the engine didn't run at all prior to me cleaning the carbs and >>>>>>>>>> it wouldn't run either after I cleaned them, full choke or not. The >>>>>>>>>> only way I could get some pop would be to spray starter fluid >>>>>>>>>> directly into the intake after removing the carbs while cranking the >>>>>>>>>> engine by holding on to the starter button. And even then it >>>>>>>>>> wouldn't run well, some cylinders would fire sometimes and once in a >>>>>>>>>> while, and the motor wouldn't really synchronize. The only problem >>>>>>>>>> the bike had prior to the day that it wouldn't start was that it was >>>>>>>>>> that the bike needed full choke for while when it was cold. Also >>>>>>>>>> more throttle (higher rpm) prevented it from stalling as easily. >>>>>>>>>> Once the bike was warm and running, there were no problems. After >>>>>>>>>> the engine wouldn't start, the first thing I checked after spark was >>>>>>>>>> the carburetors, but they actually looked pretty clean and I could >>>>>>>>>> see through all the jets and everything. I know for a fact there is >>>>>>>>>> an issue with piston ring/cylinder wall contact, because compression >>>>>>>>>> went up from 110 to 175 when I put a little oil in cylinder 1 to >>>>>>>>>> help seal whatever gap there might be. I just don't know if that low >>>>>>>>>> compression is the only thing preventing the engine from staring. >>>>>>>>>> >>>>>>>>>>> On Thu, Sep 13, 2018 at 9:12 AM Lar <[email protected]> wrote: >>>>>>>>>>> Ok, so you have spark, you have fuel in the carbs as per drain line >>>>>>>>>>> fuel but I wonder about your comment "especially at higher rpm" >>>>>>>>>>> Are you saying the bike ran rough at slower rpm? Is it possible >>>>>>>>>>> your carb cleaning may have dislodged something which is now made >>>>>>>>>>> things worse? Will the motor fire at all with the choke fully on? >>>>>>>>>>> Best of luck. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> -- >>>>>>>>>>> You received this message because you are subscribed to the Google >>>>>>>>>>> Groups "Nighthawk Motorcycle Lovers!" group. >>>>>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>>>>> send an email to [email protected]. >>>>>>>>>>> To post to this group, send email to >>>>>>>>>>> [email protected]. >>>>>>>>>>> Visit this group at >>>>>>>>>>> https://groups.google.com/group/nighthawk_lovers. >>>>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>>>> >>>>>>>>>> -- >>>>>>>>>> You received this message because you are subscribed to the Google >>>>>>>>>> Groups "Nighthawk Motorcycle Lovers!" group. >>>>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>>>> send an email to [email protected]. >>>>>>>>>> To post to this group, send email to >>>>>>>>>> [email protected]. >>>>>>>>>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>>> >>>>>>>>> -- >>>>>>>>> You received this message because you are subscribed to the Google >>>>>>>>> Groups "Nighthawk Motorcycle Lovers!" group. >>>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>>> send an email to [email protected]. >>>>>>>>> To post to this group, send email to >>>>>>>>> [email protected]. >>>>>>>>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>>> >>>>>>>> -- >>>>>>>> You received this message because you are subscribed to the Google >>>>>>>> Groups "Nighthawk Motorcycle Lovers!" group. >>>>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>>>> an email to [email protected]. >>>>>>>> To post to this group, send email to [email protected]. >>>>>>>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>> >>>>>>> -- >>>>>>> You received this message because you are subscribed to the Google >>>>>>> Groups "Nighthawk Motorcycle Lovers!" group. >>>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>>> an email to [email protected]. >>>>>>> To post to this group, send email to [email protected]. >>>>>>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>> >>>>>>> >>>>>> -- >>>>>> Colin Evans >>>>>> Cura Automation Projects >>>>>> 3405 Bluebonnet Road >>>>>> North Vancouver BC V7R 4C6 >>>>>> 604.288.2471 >>>>>> [email protected] >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "Nighthawk Motorcycle Lovers!" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>> an email to [email protected]. >>>>>> To post to this group, send email to [email protected]. >>>>>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google Groups >>>>> "Nighthawk Motorcycle Lovers!" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send an >>>>> email to [email protected]. >>>>> To post to this group, send email to [email protected]. >>>>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "Nighthawk Motorcycle Lovers!" group. >>>> To unsubscribe from this group and stop receiving emails from it, send an >>>> email to [email protected]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>>> For more options, visit https://groups.google.com/d/optout. >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "Nighthawk Motorcycle Lovers!" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at https://groups.google.com/group/nighthawk_lovers. >>> For more options, visit https://groups.google.com/d/optout. >> -- >> Colin Evans >> Cura Automation Projects >> 3405 Bluebonnet Road >> North Vancouver BC V7R 4C6 >> 604.288.2471 >> [email protected] >> -- >> You received this message because you are subscribed to the Google Groups >> "Nighthawk Motorcycle Lovers!" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at https://groups.google.com/group/nighthawk_lovers. >> For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "Nighthawk Motorcycle Lovers!" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/nighthawk_lovers. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/nighthawk_lovers. For more options, visit https://groups.google.com/d/optout.
