This weekend did we really look forward too. Mantorp Park is our home track and it is also one of the biggest races in Europe with 360 teams from Junior Dragster to Top Fuel. The fuel cars is running 1000-feet and Top Fuel Bike and Super Twin is running 1/8 mile because of the short stopping distance. The weather looks great and the grandstands were sold out early.
After the Alastaro race did we feel that now is it time to start tuning getting the performance out of the bike. We did step up the tuning from Finland trying to do our best first round out trying to get into the 8-bike ladder. There is 20 twins trying to be there.
We have been struggling with unstable idle on the bike since the time we first started it. We get it running right but for some reason does it runs bad next time we start it. The main problem is a cold wet rear cylinder which change to hot during load and the front cools down. With help of the nozzle sizes does we compensate for it and got it pretty good in Finland. But when after the first burnout is it real bad. The fuel is just flushing out of the rear cylinder exhaust pipe so we decide to stop the engine and cancel the run.
Back in the pits checking all nozzles and check valves. Re-jetting with nozzle changes, start testing many times. We were not satisfied but went out for next qualification run. It did run better now and the temperature between the front and rear cylinder were almost perfect. The plan was to do a “soft” hit and do a full 1/8 mile run.
But direct when Charley opened the throttle full did the engine misfire a couple of times and stopped abrupt. It stopped so quick that the blower belt was ripped off. The broken blower belt and bent pushrods on the front cylinder was the only thing that showed that something was wrong. Some oil smoke from the exhaust pipes as well.
This was not what we wanted. Back to the pits draining the oil to start analyse the damages. There was a lot of nitro in the oil. The intake manifold were full of oil and when the cylinder heads was removed did we realize that the front piston had been pushed down to the bottom and with help of the wrist pin splitting the connecting rod in two halves. We got the same damages at the last tests in Finland last year.
We have been struggling with unstable idle on the bike since the time we first started it. We get it running right but for some reason does it runs bad next time we start it. The main problem is a cold wet rear cylinder which change to hot during load and the front cools down. With help of the nozzle sizes does we compensate for it and got it pretty good in Finland. But when after the first burnout is it real bad. The fuel is just flushing out of the rear cylinder exhaust pipe so we decide to stop the engine and cancel the run.
Back in the pits checking all nozzles and check valves. Re-jetting with nozzle changes, start testing many times. We were not satisfied but went out for next qualification run. It did run better now and the temperature between the front and rear cylinder were almost perfect. The plan was to do a “soft” hit and do a full 1/8 mile run.
But direct when Charley opened the throttle full did the engine misfire a couple of times and stopped abrupt. It stopped so quick that the blower belt was ripped off. The broken blower belt and bent pushrods on the front cylinder was the only thing that showed that something was wrong. Some oil smoke from the exhaust pipes as well.
This was not what we wanted. Back to the pits draining the oil to start analyse the damages. There was a lot of nitro in the oil. The intake manifold were full of oil and when the cylinder heads was removed did we realize that the front piston had been pushed down to the bottom and with help of the wrist pin splitting the connecting rod in two halves. We got the same damages at the last tests in Finland last year.
Parts that was damaged was both connecting rods, front cylinder and piston, pushrods. Probably was also the main roller bearings damaged. Everything needs to be inspected and cleaned and we had the parts to fix it for Saturdays qualification but after discussion in the team what can cause the problem did we decide to not fix it. We need to find and fix the problem otherwise will same thing happen again.
Last years problem with torching out the cylinder heads was caused by faulty cam timing which we corrected with softer cam lobes that we pressed on and welded ourselves to get a perfect timing. Now we have find out that there is one more problem that needs to be solved. On our way solving the problems have also other parts been redesigned to minimize damages and also made “bullet-proof” (almost).
Example of parts is head to cylinder seal system with a o-ringed copper gasket, new ARP 8740 cylinder head studs (8 x 7/16 + 3 x 3/8), new safer ½ ARP2000 cylinder base studs that has 220,000 tensile strength, new designed lighter Venolia pistons with .017 Dykes (L-shape) top ring, now without skirt buttons that seems to work perfect in combination with the Uddeholm Impax Supreme cylinder and the Red Line WT70 synthetic oil. The new Uddeholm Orvar Supreme wrist Pins with Oerlikon Balzer Balinit Star coating is like new even after the big failures. The Uddeholm Orvar Supreme is very easy to adjust and does not move or bends even if the pushrods is bent out of the pushrod seat. And the new Uddeholm Deivar crank does stand the piston/rod failure, only some cleanup with Scotch Brite needed.
During the rest of the weekend in Mantorp did the team got time to analyse what is causing the problem and what to do about it. We did come to the ignition system. Not the components but the way it is installed in the powertrain. We suspect that the space for the distributor caps is to small so when the engine is put under high load with a lot of fuel the energy is released to motorplates and covers thru the caps and or jumping to the wrong post in the caps trying to find the easiest way to ground thru the “waste spark boxes”. These large 44-amp car mags is normally mounted with a lot of space around them and large caps just to prevent sparks in the wrong place.
During the rest of the weekend in Mantorp did the team got time to analyse what is causing the problem and what to do about it. We did come to the ignition system. Not the components but the way it is installed in the powertrain. We suspect that the space for the distributor caps is to small so when the engine is put under high load with a lot of fuel the energy is released to motorplates and covers thru the caps and or jumping to the wrong post in the caps trying to find the easiest way to ground thru the “waste spark boxes”. These large 44-amp car mags is normally mounted with a lot of space around them and large caps just to prevent sparks in the wrong place.
To get forward and see if our theory is right is a MSD electronic ignition going to be installed temporary and the mag system will be partly removed and disconnected.
This will happen the next couple of weeks and the bike will preliminary be ready for testing in Alastaro at the end of this month.
This will happen the next couple of weeks and the bike will preliminary be ready for testing in Alastaro at the end of this month.
The race in Mantorp this year was the best so far with a lot of new records in many classes. It is great to see the big interest for dragracing from younger people. Over 50 junior dragster teams did race during the weekend. The Junior Dragbikes did not compete at this race. After the semifinals Sunday did the rain come and the organizer has to stop the race 9.30 PM because of wet stopping distance and darkness.
Friday evening did the Super Twin Dragbike Association ,as every year in Mantorp with a few exceptions, invite all Super Twin Teams and some other special invited sponsors and guest for dinner. This year was special with a 20 year anniversary.
