So i just finished building my first engine, a 12a half bridge.



everything was checked and clearanced by the book etc , problem is i can only get it started using engine oil down the carby, and then the longest its stayed alive is 2-3 minutes until it just stops dead, i used all new seals and springs apex seals and corner seals out of the atkins kit.



im thinking a compression problem??? not too sure is it just because it needs to be run in? seems to foul up alot, and i haven't got it timed properly because the previous owner put gilmores on the belt.



Also the first time it started it didn't have oil but only ran for 30 seconds



Could it be the timing?



also my starter motor is very loose and seems to crunch sometimes could this be a problem?



it just has a standard nikki 4 barrel could it be a vacum of some sort??



its only running a standard points distributor, could this be the problem do i need to upgrade to electronic



it also has a after market fuel pump



any help would be very much appreciated thanks

 

sounds like you had a seal sticking out when you put your middle or end plate in . did you hear a crack when you did up your main bolts?

 

Low compression is the usual problem. A well done engine with good even used pieces should start instantly. You must get some timing marks onto your front pulley. Set timing to 20 degrees total for run-in. Points ar fine so lang as they are new and free of oil.



Check that the new fuel pump is not overpowering the carb. Stock the Niki had a return line back to the tank and ran nearly no fuel pressure. The spring inside the needles could be over powered and flood the carb. If you want to change that system, you can replace the spring in the needle with a bit of plastic tube from inside of a Bic pen. Then it will be rigid and act like a normal carb without the return line.



If you put a wrench on the crank nose and find the engine is stiff right at shutdown, then you have a problem that requires a teardown for inspection. Also check compression on both housings. Take the Shrader valve out of a standard compression gage. The oil is sealing the engine and getting you enough compression (and heat of compression) to vaporize fuel and get you a start. You should not need oil to start a fresh rotary. Compression should be over 100 PSI even with a bridge port.



Fill in your profile.



Lynn E. Hanover

 

Thanks so much Lynn for the reply



Ok so alot has happened since i first posted this, well i fitted the starter motor properly, set the timming and i have been able to start the engine about 6 times. I got it going in the weekend just gone, 2 times had it running for about ten minutes With out any oil., but it wouldn't idle for some reason, then i found that the bracket that the accel cable was loose so i tightened that, brought a brand new compression tester, but now it wont crank. it seems it has become hard to turn???? so i got my 19mm socket on my ratchet and start cranking hand, its alot tighter than it was before???



I believe this is what you were referring too



It was fine before? does this mean tear down time? i thought it mite be some of the oil left in chamber making it hard to turn.



What usually causes this? im guessing end play?



Your input is greatly appreciated, thankyou.



Oh i also have a few videos of it running. i have uploaded, i know i shouldnt be revving a fresh rebuild too high but couldnt help myself, i cut short but the end bit is pretty much how it sounded.



[attachment=47865:12a half bridge.MOV]





Ill update my profile soon.

 

Hay thanks for the reply na im pretty sure there was no crack when i torqued the tension bolts up, would it not run at all if that happened? are you talking about the apex seals?

 

Two guesses. You ran without oil and fried a bearing, and, or, you trapped the rear thrust bearing with the spacer sleeve and ruined the sleeve and bearing. Yes a teardown is needed. Sorry.



Lynn E. Hanover

 

Im pretty sure i installed the torenting bearing and the spacer correctly, i ran the engine with oil always, but i have found that my oil cooler line is twisted. would that stop flow to the bearing and internal engine parts, the twisted line was coming out of the rear iron. Im thinking that it would of not stopped flow but ratther just stopped cooling the oil. Not to sure on the oil system.



Mazdaez7

 

Normaly the line running from the cooler to the Banjo fitting at the bottom of the rear iron is the only way oil can get back into the engine. From the banjo fitting into a vertical gallery that includes the oil pressure sender, then on up the the filter pedistal, then from the filter back down to the main gallery and a downward drilling to the rear main bearing and rear excentric and rotor. The main gallery is made up of the top left dowel gallery and runs to the front iron and front main bearing and excentric and rotor bearing. If that line is blocked there is no oil flow to the bearings. The high pressure would then fail the front cover "O" ring or open the front cover relief valve set at 140 pounds. This seldom happens, but it can.



You can check both front and rear main bearings by pulling the stationary gears out for inspection. Just don't turn the crank while the stationary gear is out of the engine.



Lynn E. Hanover

 

I pulled oil lines off in the weekend, oil was dripping out of twisted line so oil was passing through, i replaced both oil lines with brand new lines. filled her back up with oil. I just recondition the starter motor with new brushes,so i tried to start it up. the started motor died, its completely dead, opened it up its a through away. I put some fluid through the carb and turn with ratchet to clean up and it seem to free the engine alot.My friend just so happened to be at home so we tried a tow start. It fired up first pop , unhooked the tow rope and i took it for a long drive to try wear in the new seals. Did not over heat, was running fine, we adjusted the idle screw and had it idling which made driving alot better.



But there was one problem, when running on the primary ports the car was very sluggish, and had little to none acceleration, had to rev it quite high to take off. But when it hits secondary port open car runs fine, have no idea why this is? could this be something to do with the carby or is it a half bridge thing?



The starting problem i found also was coolant leaking into the combustion chamber, Im guessing through the relief's in the rotor housings for the bridge port, i got a product called seal well, they little cubes you break up and put into the coolant system, seems to have done the trick, no more leak.



Im just waiting on a new starter to have another play with it lol. :-)

 

Let me know if it started cauze i am i the same situation