Bridgestone Motorcycle Parts Discussion Board
General Category => General Discussion => Topic started by: mrjones on June 16, 2017, 09:26:07 AM
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hello all a new member here, Marcus from wakefield in the uk,ive just finished a full rebuild on a 350 gtr but i cant get it to run,well it did start but only for a few seconds, its sparking and the carbs are clean and set to the manual specs, when i kickstart it it clicks as though the plugs are rested on the head checking for a spark and it kicks back now and then,( do they all do that?) the carbs are not in the best shape (float bowl pin lugs snapped and soldered back on ,not by me,but the float heights are correct 15/16ths? ) before i get a new set of carbs is there anything else i should know?
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Marcus Make sure the ign is correct, With K/S kick back I think you have an spark issue. The K/S system is on the weak side, so be careful.
Weak spark or wrong timing is most of the ignition issues, with weak spark it will fire plug outside enigne but no when under compression.
On a side not what is the compression of this rebuild, what about crank seals? Have them been replaced correctly?
Sam Keys
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hello Sam thanks for the reply i set the timimg as stated in scotts bridgestone manual, took the bolt out of the left crankcase side etc., but i will double check it, i dont have a compression tester but the compression is quite high going by the pressure needed to kick it over i didnt change the crank seals but again they seemed ok .
Something else i was thinking of is, would it matter if the points were "upside down" should the condensers be at the top or bottom of the points plate? mine are at the top ,it came like that, although ive stripped and rebuilt the generator since then, i thought to leave it "as was" , although ive never had it running.
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The 350 alternator/points/condensers should be oriented as shown in this photo:
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Hi Marcus,
Brian in the UK, welcome to the site.
As you are likely aware, could be any number of things. Are you happy fuel is getting to both carbs. Fuel tap cleaned out ? Choke plungers seating properly in off position ?
Two other possibilities that you might not think of:-
Are disc valves installed correctly. Easily checked, intake port should be open with it's piston at TDC. View through carb. They can be installed 180degs out of sync..
Mikuni carbs have a starter jet in the bottom of the float bowl. It's at the bottom of one of the tubes cast into bowl and has a slant drilling from the main bowl. Check they are clear. Jet is very small diameter and can't be removed.
Keep coming back to us, if no improvement, we'll get you running,.................. eventually ;D ;) Brian.
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Just some more things to look at:
You said you heard a "click" when kicking, is the spark jumping to ground somewhere on the spark plug wiring?
Sure timing is ok? Points should OPEN as timing pin drops into crank dimple.
An occasional kick back is not unusual, since timing is fixed and 25 deg. before tdc. (Can happen as crank speed drops after a good kick.)
Rotary valve timing OK?
Getting fuel? You could try a small squirt of gas into a carb just to check.
Good luck!
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If you haven't yet, make sure the correct plug is firing as the piston comes up to TDC. It's easy to get everything correct, but have the wrong plug firing.
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Karl / Marcus,
As an afterthought, an alternator fitted upside down, would trigger the wrong set of points unless the wiring was swapped over somewhere to compensate. That could very well be the problem here.
Brian
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thanks for your input everyone, many things to think of here but i will try them one at a time until it runs, i will keep you posted!
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Marcus,
I was going to say, simply turn the alternator body through 180degs and retime before doing anything else. But, I believe you would have to remove the alternator from the engine to do that, requiring the right engine side to be stripped to pull off the drive gear. ( With the alternator still fitted, there may not be enough clearance under the case to allow the slotted lug at the back or the cable exit grommet to pass underneath. You're snookered whichever way you turn it >:().
So leave that for time being but check the correct plug is firing at TDC as Karl stated above. (Swap the black/white wire connections at the coils or the connectors behind the battery box if you need to change over) That will take one potential issue out of the equation and may get you running.
When you do swing the alternator, note there should be a spacer fitted between the slotted lug and the crankcase when bolt/washer, items 15&16, Dynamo page, in the parts manual are installed. For reasons best known to BS the spacer is shown, item 2 on the crankcase parts drawing and is easily missed.
good luck, Brian.
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Also make sure the cover over the points is not able to touch the soldered ends of the condensors.
That will short out the points if they can touch, I'm not the only one that has black electrical tape on the inside face of the cover to make sure there is no electricity going down the wrong path.
Try starting it with the points cover off to see if that changes anything.
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hello all , ive had a busy few days, ive turned the alternator(generator) thru 180 degrees reset the timimg and points still no spark! checked the battery ,flat! as its a gel battery a standard charger wont work so had to take it to a dealer, one thing i noticed was the rear wheel turning as i kickstarted it (, by hand with the plugs out and exhaust off), is this right?
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If I remember the back tire can start rotating a little after idling on the center stand, but I don't think you should see much rotation when trying to start it.
Do you have a working neutral/5th gear light on the tach gauge?
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Because it's a constant mesh transmission, all the gears on the input shaft drive the mating gears on the output shaft by friction on the shaft, even when it's in neutral. The friction on all those gears turning on their shafts can produce a definite rotation of the rear wheel when it's up on the center stand, even in neutral.
You probably were able to spin the motor fairly fast with the plugs out, so I'm not too surprised you saw the rear wheel turn.
Try rotating the rear wheel in neutral. If it turn's fairly free, it's probably normal. If the rear wheel won't turn without turning the engine, either it isn't really in neutral, or there is a problem with the transmission.
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Marcus,
I struggled to find a charger suitably for our relatively small 6amp/hr battery, most have a too high charge rate.
Would recommend the Optimate2, 12v, 0.8A charger which will handle STD, AGM, GEL and EFB batteries. A fully automatic, intelligent charger which can also be left attached over winter to maintain your battery. Available on the internet for about £37 ($44).
Do you know why the battery went flat ? After 50 years, the original selenium rectifiers are notorious for allowing the charge to leak back, while the ignition is turned off. There are several good posts on the site showing you how to make a low cost modern rectifier, maybe someone can provide a link.
Brian
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Today i got my battery back refitted it and checked the spark, bright purple strong spark, plugs back in and ..... nothing!! wasnt even trying to start! back to the drawing board and try some of the other things suggested.
As for the neutral light 5th gear indicator i am missing the copper "connector" and the black unit with 2 wires coming from it is cracked, yes its leaking oil but i wanted to get the bike up and running and find every last thing i need before sending for parts, it takes time and the uk government taxes every parcel!
I didnt know the rectifier could "steal" charge from the battery ,i was looking for an earth short! which i cant find, however for now ive disconnected the earth lead and will get an up to date rec/reg and an optimiser, but first i want it running!
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Another thing you might try if you think the plugs are actually sparking when in the cylinders, I like to shoot a little model airplane fuel (10 or 15% nitro) into the carb. If you are anywhere close to having the proper fuel/air mixture along with spark the model airplane fuel (made for glow plug engines) will give you hope. If you leave the fuel lines connected to the carbs you can fill those with model fuel and get 5-10 seconds of run time.
When you are testing the spark plugs removed, are you grounding them to the engine or the frame?