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Discussion in 'Other Projects - Other Bikes (non 250's)' started by kiffsta, Sep 7, 2019.
It's going to be a shame to get it dirty
Mr BB ... a British bikes best friend ...
Positive earth - aaaaaarghhh!
Wired up the electric and everything works as is should , that is a big win for me
Fitted up my electronic ignition , I have spark
Only another 2 weeks till my exhausts arrive
wonderful.should be good for may 2nd. may win top suzuki!8 weeks to go.
Mate, you're already way ahead of my electrical skills! Good job. Are you planning to take the bike to the National Rally?
I am hoping to take it to Toowoomba, it is my sons Birthday on the 1st so I might just come for a ride up for the show and shine , not sure yet
I am just waiting on some new cables from the Netherlands and my pipes from the UK then I should be sweet
Your son is in good company with that Birthday Chris
That's why they call it white mans magic - you are now officially a qualified Magician
Following your GT380 resto with interest . It will be a beauty. Hope you are not neglecting the old T500. Looks as if a few more $$$ spent on the 380 than the Titan. I bought a new 1973 GT550K, replacing my T500J - a disappointment, until replaced in 74 with my first foray into 4 strokes and Ducatis- an860GT. Keep the photos of the 380 coming.
Hey Chris, good to hear from you.
things have come to a crushing halt , I hooked up the old exhausts and attempted to start the bike. After half an hour of kicking it , I had a few coughs , But it would not start and the plugs were dry. I removed a carburettor and put my hand over the carb boot and kicked it , the amount of suction was quite low ,
It is as if it can’t suck a charge of fuel through.
I ran compression tests on each pot and I get 125 psi cold across all 3 which is pretty good compared to a couple of other guys I know who have just built gt380 engines.
I have made my own 2 Stoke leak down tester and have 6 psi going into the carb inlet , I have sprayed soapy water around the motor and there are no bubbles from the cases so I think I can rule out that the cases have leaks. To be fair , I am a bit lost as the timing is spot on.
I also removed the electronic ignition and put the points back in to rule out ignition issues. Things are a bit quiet at the shop ,
I might put it back on the lift and work through and try and work out what’s going on.
good news is that my pipes have shipped from the UK
Dumb question - only two wires coming from the ignition plate, so the one single coil fires all three plugs three times per revolution?
So it cannot be mistimed for the wrong plug/cylinder
The Boyer kit fires all 3 coils at once , hence the 2 wires , wasted spark system
The exhaust aren't blocked? Crank seals ok? Though I wouldn't think all 3 at once. The exhaust ports seal by the piston skirt, so if the pistons are dry it may just leak past. With the plugs out there should still a lesser compression stroke as the piston goes down. Give us a call if you get stuck, I'll see if I can help.
I did check the exhausts and they are not blocked , the crank has been rebuilt with all new seals and bearings
I have spoken to a few old school
Mechanics who have lots of 2 stroke experience , there was a suggestion of using a roller starter to see if I can get get the motor spinning faster than the Kickstarter will generate: one of my customers has one and is going to drop it off
I haven't followed this long enough so I'll ask. Are you using standard coils or Boyer ones ?
I struck a similar problem recently on a Honda racebike when changing ignitions. It had used a Boyer which had failed so I made up a similar setup - twin lead coil firing twice every revolution with a magnetic trigger.
I found it was very sensitive to coil primary resistance. The same setup firing once every revolution worked fine with a 3ohm coil.
Twice every revolution needed 1.8ohm coil. The Boyer one was around 2.0 ohms.
The 3 ohm coil would fire when the engine was turned over - plugs out in the air - but under pressure, no way.
I know some of the early CB750 conversions (from points to aftermarket ignition) had issues. Only way to prove it would be to go back to standard GT380 ignition system. From a casual observer point of view, it sounds like that engine is mint and should fire up without any issues.
what coils would you recommend ? , mine are 45 year old OEM ones, I have been looking and it is mostly cheap Chinese crap available
Dirt bike coils?