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Post by paydem on Sept 23, 2018 12:29:27 GMT -5
Engine:
Minarelli Horizontal AC, long case
70cc BBK (un-marked)
Tecnigas Silent Pro exhaust
Motoforce 17.5mm PHVA carb, jetting: 85 main, 38 pilot, jet needle 3/5, air screw 2.5 turns out, automatic choke
Stock airbox with snorkel
When the engine is cold, it won't idle. The choke works, it just puffs out more smoke, but won't idle. When the engine is hot and the choke shuts off, it sometimes idles at ~2k RPM for about 5 seconds and dies. When tuning the carb, it idles fine, doesn't puff out lots of smoke, doesn't bog, the rpm's don't hang up. I can kick it one time without giving it any gas and it starts fine.
I can let the engine cool off for about 5-10 minutes after tuning, and it won't idle again. And then again, after a 10-15 minute long ride I stop, the engine can idle for up to about 10 seconds before dying. The highest RPM's seems to be around 2-3 turns out on the air screw. I already tried dropping the jet needle up or down.
The engine doesn't have any leaks, the carb and airfilter is clean, the compression is fine, I run 95 octane with 50:1 premix. Any ideas?
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Post by 90GTVert on Sept 23, 2018 22:30:37 GMT -5
Check the float height. Maybe it's off and affecting idle. Turning the idle speed screw in a little doesn't let it idle?
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Post by paydem on Sept 24, 2018 11:33:55 GMT -5
Check the float height. Maybe it's off and affecting idle. Turning the idle speed screw in a little doesn't let it idle? Alright I think I kind of lied here a little bit because I created this post after tuning it yesterday and didn't even test how it behaves when cold. So today it started and idled when cold, but after riding for 5 minutes it idles high and the clutch almost starts engaging. Also after letting it cool down for 5 minutes the idle comes down, and I need to give it some gas to get it started. After all it's far from perfect, I can't adjust float height since the float is non-adjustable. I can set it to idle at all times, but when hot, the idle is too high. What's strange to me is that when cold, the idle is lower than when it is hot. The choke works fine but it starts picking up RPM's when it warms up. It should be other way around, right? |
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Post by 90GTVert on Sept 24, 2018 12:44:15 GMT -5
Sounds like it's lean on low throttle. Warms up and needs less fuel and starts hanging or idling higher. 1st step from here for me would be to richen the idle mixture screw till it stops idling high once warm and then adjust the idle speed as needed so it can stay running at all times.
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Post by dexameth on Sept 24, 2018 14:01:40 GMT -5
Check the gaskets on all your intake stuff and make sure your throttle cable is sealed at the entry point to the carburetor. I agree with the "too lean" concept.
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Post by paydem on Sept 24, 2018 14:28:47 GMT -5
Check the gaskets on all your intake stuff and make sure your throttle cable is sealed at the entry point to the carburetor. I agree with the "too lean" concept. There's no leaks on the intake, carburetor cap is sealed but the throttle cable has a loose fit on the cap. I don't think it's a big deal, probably I just need to tune it better. Will try to do it once the skies clear up, thanks for the help. |
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Post by geoffh on Sept 24, 2018 14:54:23 GMT -5
Errmkk,you lost me when you fitted the bigger carb :)but if this is your jog the cable needs to be snug on mine there is an adjustment at the carb end and an adjuster at the twist end both need tweaking to get the best from it.
Geoff
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Post by q on Sept 24, 2018 19:12:27 GMT -5
Classic Room #101 Group "A" Crank Seal Leaking, one thing consistent about a leaking crank seal is no matter what you do to the tune it will always give you a inconsistent result. and that s what you goy goin on...
Ya just pull it, throw it away and install a new one..
Good Luck
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Post by harleyracer59 on Sept 30, 2018 22:23:31 GMT -5
Classic Room #101 Group "A" Crank Seal Leaking, one thing consistent about a leaking crank seal is no matter what you do to the tune it will always give you a inconsistent result. and that s what you goy goin on... Ya just pull it, throw it away and install a new one.. Good Luck while this is normally true, id suspect the carb. put your old carb on and see if this problem is still there. if not its a problem with carb. if still there then id say check youre seals. its process of elimination. seals were theoretically good before bbk and carb. they should be good now. if not. id also make sure theres no debris in the case from installation. |
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Post by paydem on Oct 1, 2018 9:39:37 GMT -5
Whatever, air screw tuning and dropping the needle clip one position higher fixed all my issues. Now it idles at all times. I guess I was too lazy to put more time on the engine and instead posted here.
I'll be more patient next time.
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