August 28th, 2021, 08:21 AM | #1 |
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Help with a 1986 Ninja 250 that will not rev up
I have a 1986 Ninja 250 that I bought from a friend. Long story short this bike has been raced and abused. It was also highly modified for that purpose. I have been working on getting it back to stock. one of the problems that I am having is that It will not rev over 5000 RPM's or if it does it bogs really bad. Very slow to come up to speed. Not sure if I used the right jet needles in it or not. The ones that I am using come from a rebuild kit. The ones that came with it were the clip style but it does not want to start when using those.
Took it out for a quick spin the other day and a mile down the road it lost power and died. Not sure what to check and work on at this point. In addition to it not revving up, there is a popping/ticking sound coming from the right upper side of the engine that only happens when gassing it up. At idle it is fine. any help with these problems would be greatly appreciated. Thanks Tom Last futzed with by tomsninja2020; August 28th, 2021 at 08:43 AM. Reason: added info |
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August 28th, 2021, 08:37 AM | #2 |
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Tom-
On the 32mm, metal slide equipped carbs....non-adjustable, original needles are N52H in lh carb, N52I in rh carb. Are you using these? With what main jets? Frankly, kit tuning components are notoriously "copy-cat" crapshoot, may work, may not. Kit is meant for your year 250? Or a more common later model? Note 32mm metal slide carbs only used in 86-87 models. Check valve timing/clearances as yet? Truly clean carbs/circuits?
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August 28th, 2021, 08:38 AM | #3 |
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Hi Tom, welcome to the board!
The first thing you need to do is make sure the carbs are spotlessly clean, including the small, nearly hidden passages, etc., and also return them to stock, with genuine Keihin stock size jets. Trying to get it running right with aftermarket parts will be a long and questionably successful job. If you like, Ducatiman here on the board is expert at doing this, and can get them into like-new condition quickly. Edit: He posted while I was typing. |
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August 28th, 2021, 08:50 AM | #4 |
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I think the kit that I got was for the '88 ninja 250 instead of the '86 because I was not able to find the '86-'87 EX250-E rebuild kit. So do you suggest that i buy the correct needles? The spark plugs were black and oily from running extremely rich I believe.
How do you tell the difference between the LH and RH needles? |
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August 28th, 2021, 09:03 AM | #5 |
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no good, 88 and up are 30mm, 86-87 are 32mm. Different innards required. Assure your mains are correct, pilots too if you used from the kit.
pilots #35 mains 108 (could vary slightly) Long ago, i sold a set of these early model 32mm carbs to member @Ghostt.
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August 28th, 2021, 09:05 AM | #6 | |
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Quote:
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August 28th, 2021, 09:14 AM | #7 |
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YES....assures a known starting point for factory, like new running performance, Provided all your other reported work is ok. Please tell me you've retained the airbox?
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August 28th, 2021, 09:21 AM | #8 |
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Hi Tom, in addition to non-compatible rebuild parts mentioned above, you may have petrol delivery issues from tank to carbs. Make sure tank vent-hose is not clogged.
Also make sure petcock vacuum diaphragm works. Test by applying vacuum to petcock and measuring flow. Should flow freely from petcock. |
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August 28th, 2021, 09:33 AM | #9 |
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i recently restored an ex-racer 1st-gen 250 too!
had to completely disassemble carbs down to every last nut, bolt and individual part and scrub all hidden secret petrol passages. http://n4mwd.blogspot.com/2013/10/se...-passages.html Last futzed with by DannoXYZ; August 29th, 2021 at 04:08 PM. |
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August 28th, 2021, 01:52 PM | #10 |
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August 29th, 2021, 05:30 AM | #11 | |
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Quote:
thanks Tom |
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August 29th, 2021, 08:56 AM | #12 |
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so you've got stock airbox back on it now?
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August 29th, 2021, 08:57 AM | #13 |
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need answer to above question prior to opining on this one.
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August 29th, 2021, 01:07 PM | #14 |
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not yet because of having to carburetors off so much
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August 29th, 2021, 01:14 PM | #15 |
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when I try to start it that way it pops and sputters but does not start. So i guess that is still to rich? My scooter is a lot easier to work on then this. I guess that want happens when you buy a used motorcycle that sat since 2009. I did have it going for a while but I could not get past 5,0000 rpm's the engine would just bogg or die. I have a limited amount of resources that I can work with as well as funds. So any and all help that you can provide me would be greatly appreciated.
thanks Tom |
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August 29th, 2021, 01:32 PM | #16 |
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If you think it's too rich, with the starter lever in the run setting (off) hold the throttle open and crank the engine. That will clear out excess fuel.
If that doesn't get it started, it's because being too rich isn't the problem. |
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August 29th, 2021, 01:52 PM | #17 | |
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Quote:
I would pull the carbs, throw away any parts from the kit, and replace them with stock OEM parts. The carbs should be gone through carefully and thoroughly. The stock 38 (EDIT: 35?) Pilot jets are just fine. Your idle mixture adjustments may be more open than normal, somewhere in the 2.5 to 3.0 turns out most likely. Use the stock needles in their proper position per ducatiman. You may want to add 1 small shim to richen the mid-range if you have pods and a pipe - but don't go overboard. A Main Jet in the range of 108 should be close. Use only OEM jets, and richer isn't better. Check that you have the "collars" (Needle Jets) in the carbs (https://faq.ninja250.org/images/e/eb/Jim_carb_2.jpg) . They stick up into the venturi from the bottom, and fall out when you disassemble the carbs. Look over this section for more info - https://faq.ninja250.org/wiki/Intake When you get finished, and before you try to start it, you may want to install new plugs. That would give you some idea of what's going on if you are still having issues. Be careful of counterfeit NGK plugs from no-name online supplies. You may want to check the valves while you are at it. It's not going to run if they are way off - https://faq.ninja250.org/wiki/How_do..._the_valves%3F Last futzed with by jkv45; September 1st, 2021 at 07:08 AM. |
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August 29th, 2021, 02:55 PM | #18 | |
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Quote:
I started racing these bikes 5-yrs ago at tail-end of 35-years of trial & error development between millions of 250 racers. Those who've come before me have compiled extensive list of upgrade-mods for these bikes. Even though rules allow it, not a single racer amongst MILLIONS used pod-filters because they provide zero gains in performance and introduces too many problems. Stumbling and surging mid-range is biggest issue, not to mention instability in cross-winds. Racers are lying cheating bastards who'll do anything and everything to gain an unfair advantage over their competitors. They only use what works, pod filters don't. Need to test these with airbox installed: 1. Do clearing test outlined above. Then start bike with no choke. Does it start and run better? 2. Do same clearing test again. Start bike with full-choke. Does it start & run better? 3. what procedure did you use to clean carbs? 4. which one of these needles looks closest to one you have in bike? Last futzed with by DannoXYZ; August 29th, 2021 at 04:00 PM. |
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August 29th, 2021, 03:34 PM | #19 |
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"bike sitting since 2009", modded with unknown carb "kit" internals.....
I'd suggest a pro carb clean & setup, returning to all OEM stock internal tuning components on carbs .....installed WITH factory airbox....a known starting point.
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August 30th, 2021, 08:49 AM | #20 |
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1 and 3
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August 30th, 2021, 04:31 PM | #21 |
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We're trying to gather information to help you, so please give data that's necessary to troubleshoot.
1. Ok, #1 adjustable needle should've come with your DynoJet kit. What main jet sizes came with this kit? 2. #3 needle has more gradual taper at tip than DynoJet needle? Can you take photo and post here? Are you able to zoom in and get clear view of numbering on needle? 3. What main jet size came with bike? 4. what brand 2-1 exhaust is on bike? Please post photo 5. have you verified petcock flows petrol continuously when vacuum is applied? 6. have you confirmed that needle collars are installed with correct orientation? Internally, there is tapered end. This should face away from main jet and towards carb-venturi / needle. 7. what procedure did you use to clean carbs 8. measure all valve clearances and post here. There's basically 3-4 areas of concern that may be causing you problem. Most likely you have them all to certain extent. Your data will point towards ones to address first. |
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August 30th, 2021, 05:56 PM | #22 |
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The Jet needles, main jets and the pilot jets that came with it are all unreadable , sorry I wish I could be more hopeful here. It did run last week but would not rev over 5000 and most of the time after 10 minutes of running it would die. Petcock does work as expected.
I replaced the pilot jets and main jets with ones that came with the '88 kit since they don't make a kit for the '86 ninja. I did just today ordered the correct jet needles for the left and right hand carbs. I put as close to stock mufflers as I could find along with the air box. Valves have been checked and adjusted per the manual. Checked that the timing chain and camshaft markings all are in line and they are. I had taken the engine apart a month ago to replace a rod bearing. |
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August 30th, 2021, 05:57 PM | #23 |
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jet needles that came with the bike.
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August 30th, 2021, 08:02 PM | #24 |
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Hmm, dying after 10-mi. still sounds like fuel-flow problem...
well, you should bundle ALL parts from DynoJet kit back in box and return it. Cannot use DynoJet needles with factory jets and factory needles with DynoJet jets. Now that you're getting factory needles, we need to find out what size jets you have that came in those carbs. Hopefully factory sizes. Last futzed with by DannoXYZ; August 31st, 2021 at 10:11 AM. |
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August 30th, 2021, 08:26 PM | #25 |
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August 31st, 2021, 05:52 PM | #26 |
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Update:
I put the air box back on and found out that I had fouled spark plugs from running rich. put in another set. Put the original #35 pilot jets that came with the bike in and that fixed most of the low end issues. The ones that I had were #40 and way to rich. The upper throttle/RPM range is still suffering from the rich condition due to the wrong jet needles. I should have the right ones by Friday( one from CA and the other from MS) Thank you everyone for the help thus far. Tom |
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September 1st, 2021, 02:02 AM | #27 |
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Ordered #108 main jets to fix the rest of the issues. I will report back when everything is installed. Again thank you for the help.
Any Ninja owners around south central Minnesota let me know. Thanks Tom |
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September 2nd, 2021, 02:38 PM | #28 |
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You're welcome Tom!
Interesting data you're providing us. Helps build up database of known facts for searches and troubleshooting in future. Please take photo of your new factory '86-87 needles compared to ones that came on your bike. I suspect they used ones from different model-year. Which would explain some of your mid-range issues. I wished I had datalogged some runs with my wideband before selling. Would be interesting to have actual AFR data of factory configuration. |
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September 2nd, 2021, 03:43 PM | #29 |
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are #108 main jets going to be to lean for here in Minnesota. Elevation is 1,158' In my 150 scooter I run #125 but that is a gy6 150 engine so not sure how much difference that makes. I just don't want to have to chase jet sizes till I find the right one that works.
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September 2nd, 2021, 09:07 PM | #30 | |
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Quote:
Also you got Keihin jets right? Other brands may have #108, but they are actually different hole diameter. |
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September 3rd, 2021, 05:02 AM | #31 | |
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September 5th, 2021, 04:11 AM | #32 |
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I got the bike to rev up a little better but it still has an erratic idle to it and the carb slides do not seem to lift. It had good acceleration up to 4000 RPM but after that it just was flat. Can I pull the air box out of the way enough to check that or what would cause them not to lift. When I open the throttle it is sputtering like it is not getting enough fuel to keep going. Did find pin holes on the slide diaphragm and repaired them but I ordered a new set to be on the safe side.
Thanks Tom |
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September 5th, 2021, 06:36 AM | #33 |
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using the correct needles and mains?
contrary to black, plastic later model 30mm slides, your 32mm metals require "dressing" if not a certain degree of polishing, with special attention given to their guides (in the bodies). Lift can be checked/confirmed using moderate compressed air. (within my service I perform this routinely on EX500 carbs that use metal slides) The return springs are correct length, not causing binding in any way? Note some jet "kits" require cutting of springs, a no-no if returning back to OEM spec. 35 year old diaphragms, if never replaced, should be, especially those with holes of any size. "Erratic" idle? IF your carbs circuits are truly clean, are synched and pilot screws set correctly (with new orings)....it should idle decent. Furthermore, blocked transition ports could be causing some issue with reluctance to run over 4K threshold. I'll submit your carbs are not truly clean. You've confirmed adequate valve clearances?
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September 5th, 2021, 02:18 PM | #34 |
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What are the correct valve clearances? I am using .004 inches for intake and .006 inches for exhaust.
also were does the engine pull fuel at idle? is it the transition ports or the area around the mixture screw? The thing that I am not understanding about this engine is this. My 150cc scooter engine runs just fine. Idles like it is supposed to and everything. This engine does not idle correctly, is hard as hell to start and keep running. If i do get it to run and in gear I cannot turn the throttle more then a quarter turn or the engine will bog and or die. Like I said before, new rings were installed last year but have yet to really seat and break in. Compression for both cylinders is around 90 to 100 psi with the new rings and cylinder honning. New head gasket, new rod bearing on #2 cylinder. Still makes a lot of noise from that side of the engine. CCT has new springs and bearings in it. I am at a loss here because I have put so much time and effort into this bike and it still will not run right. thanks Tom |
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September 6th, 2021, 05:05 AM | #35 |
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[QUOTE=ducatiman;1293350]no good, 88 and up are 30mm, 86-87 are 32mm. Different innards required. Assure your mains are correct, pilots too if you used from the kit.
pilots #35 mains 108 /QUOTE] Can I use #40 pilot jet as that is all I have right now? |
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September 6th, 2021, 06:03 AM | #36 |
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You had posted previously...."The ones that I had were #40 and way to rich."
2 sizes over the correct 35...you tell me. Wait till you get the correct jets. AFA valve clearances.....you've got no manual? An underseat sticker present perhaps? Your transition ports may be clogged, due to way overich #40's in there, or existing varnish present. In addition to suspect slide action....
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September 6th, 2021, 11:02 AM | #37 | |
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If not, reach in there with your fingers and help lift slides up as you increase throttle. Does it redline now? If so, you've got slide issue. New diaphragms may help. May also need to scrub out vacuum-ports from beginning to end. Also make sure vacuum-chambers are sealed. |
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September 7th, 2021, 06:46 PM | #38 |
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Just a quick update: #35 pilot jets installed, #108 main jets (i Think), correct needles with no shims. Carbs cleaned. Fuel mixture screws 2.5 turns out. Seems kind of boggy and I have a hanging idle problem. I can touch the throttle and the RPM will hang at a high idle even with the idle adjuster turned down. I think that is a lean condition right? So how can i fix it? I did notice that there was a tiny o-ring missing from the air cut valve assembly. Does any one know what size it is and if I can go to my local hardware store and get a new one?
The Taiyo Giken Petcock is leaking gas in the fuel line even in the on position. I would like to replace it with a new one, but I am not sure want to get. The one I have has that special silver disc on the petcock lever and I cannot seem to find another petcock that it would fit. If someone could help me with this I would appreciate it. Thanks Tom |
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September 8th, 2021, 04:06 AM | #39 |
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"#108 main jets (i Think)" huh? OEM Keihin jets are marked
AFA hanging idle....are carbs correctly synched? Bowl fuel levels set correct? Pilot screws may need further fine tuning, setting at 2.5 not perfect for all. I'll get back on the "oring' size (its actually a "D" ring, but a oring could be subbed) Is it able to freely rev now?
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September 8th, 2021, 06:01 AM | #40 |
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Hanging RPMs usually mean there is a vacuum leak somewhere.
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