Poor performance

Technical questions and answers

Poor performance

Postby rubberfingers » Tue Jul 28, 2009 7:19 pm

Hi there I am new to this board - I hope you can help me.

I have a TZR250 2MA which I have owned for 12 years, it has been laid up for the last 18 months and I have been getting her back on the road. I have done a lot of work to her and she is now MOT'd but I have a problem in getting her over about 95mph.

The engine runs fine and will readline in every gear and is as fast as ever to 80/85 when it starts to struggle a little. It will get to 95-100 when really pushed but no further.

I have replaced the following - Plugs, caps, HT leads (coil with an aftermarket one which had too much resistance so I put the old one back in), stripped and cleaned the carbs, checked the reeds, new air filter, decoked the exhausts, checked the powervalves, raplaced the tank filter, replaced the fuel lines etc etc

I have noticed that the pick up coil appears to be out of specification - the manual states the resistance should be 94-140ohms - mine measures 238ohms which is 2x times it should be. Can anyone advise what effect this will have on my ignition system - could this be the cause of my poor high speed performance (hard to get over 100mph)?

Can anyone offer any advice on what may be causing this problem - many thanks in advance
rubberfingers
Pit Bitch
Pit Bitch
 
Posts: 10
Joined: Tue Jul 28, 2009 6:23 pm

Re: Poor performance

Postby Higgsy » Thu Jul 30, 2009 11:18 am

Hi

The pick up coil being over resistance is not unusual in my expierience, mine on my race bike is, but not as much as yours, I guess the only way to eliminate the coil as a possibility is to swop it with another one and see what happens. As the bike seems to redline in other gears presumably without missfiring then i wonder if this is a mechanical issue. You have checked the powervalves, are they correctly set up? Best to stick your fingers up the exhaust port and check the position as well as relying on the carrier line up hole. Are the powervalves working in unison, the connector piece has a habit of wearing badly. What condition are the pistons and bores in? If it's worn then the symptoms you describe would fit.

Higgs
Higgsy
Spammer
Spammer
 
Posts: 2009
Joined: Tue Mar 17, 2009 5:50 pm
Location: Medway Marauder

Re: Poor performance

Postby rubberfingers » Thu Jul 30, 2009 11:38 am

Hi thanks for the response.

I have not taken off the head to visually check the bores and rings but I dont think there is a problem with them. I have done a compression check (on a cold engine) and got 107psi and 109psi which I beleive is quite good? The compression feels good also and there is no blown back on the pistons from what I can see in the exhaust port.

I have checked the valves by using the line up hole as they appear to be adjusted ok - also I have removed the right hand cover and can confirm both valves rotate when the ignition is switched on. They also rotate at around 7000rpm when I did a (noisy!) check in the garage.

How do you physically check to check they are alligned correctly - how should be lined up with the top of the exhaust port?

I am really baffled by this asI said it not miss and redlines in every gear until I get to 5th where is seems to stick about 9500rpm (95mph ish).

thanks again
rubberfingers
Pit Bitch
Pit Bitch
 
Posts: 10
Joined: Tue Jul 28, 2009 6:23 pm

Re: Poor performance

Postby No7 » Thu Jul 30, 2009 11:56 am

As Higgsy says - Manual check - Remove exhausts and cycle the Powervalves - stick your fingers up the port and they should be fluch with the top of the exhaust port - check both sides - They both may rotate but due to wear and tear in the linkage and PV ends they can be out of sync

While you are there use a torch and have a look up ports at front of pistons and bore where you can by rotating the engine

Fish
User avatar
No7
Site Admin
Site Admin
 
Posts: 1480
Joined: Fri Feb 06, 2009 9:40 pm
Location: Reading, Berks

Re: Poor performance

Postby rubberfingers » Thu Jul 30, 2009 5:42 pm

I think you could be onto something there. I removed the exhaust pipes (again) today and set up the left hand side valve - it operates fine and lines up flush with the top of the port when it is fully open (when closed it moves upwards at the front of the port nearest the exhaust and downwards at the rear next to the pistion - I presume this is the correct way round?).

However the same cant be said for the right hand power valve. The valve rotates but does not have as much movement range and appears to be a fraction of a second behind the other one. When it is fully open there is a few mm gap i.e it is a few mm recessed upwards into the head and not flush. When I remove the right hand cover I can then turn the valve slightly by hand until it lines up flush with the port. When I turn on the ignition again and they cycle it does the same thing again - does not line up 100%.

I presume because the right hand valvue is not fully opening this will be effecting my performance - would a few mm make that much difference?

How do I cure this problem - is it a problem with the middle linkage or something else? Can I take out the valve without removing the head and barrels, if so how?

thanks again
rubberfingers
Pit Bitch
Pit Bitch
 
Posts: 10
Joined: Tue Jul 28, 2009 6:23 pm

Re: Poor performance

Postby No7 » Thu Jul 30, 2009 11:49 pm

The valve rotates into the barrel and then out - when the holes lines up on the marker on the left barrel the valves should be flush with the top of the port - if you can turn the right hand valve without then left hand turning I suggest there is play in the linkage and wear on the valves that it clamps to.

You cannot remove the valves without taking the barrels off or at least one of them - You can remove the linkage depending on state of bolts holding it together .

I guess if you wana check the power - fix them open - disconnect the cables and take it on a long road - if it revs clean past your issue you know the problem is the timing/movement of the PV's

Fish
User avatar
No7
Site Admin
Site Admin
 
Posts: 1480
Joined: Fri Feb 06, 2009 9:40 pm
Location: Reading, Berks

Re: Poor performance

Postby rubberfingers » Fri Jul 31, 2009 12:37 pm

Today I made up some thin inserts from some aluminum for the holder and put it all back together. There is now no free play at all in the valves and they both operate exactly the same.

Took the bike out for a quick test run and it definatly seems to be better - while I could only get to 95 before (at a push) it now went to 105 before I ran out of straight road and still appeared to be pulling fairly well. I am going to assume if I had more road it would have gone quicker as it definatley was still pulling.

I will try and take it out for a longer run at the weekend to make sure but i *think* this may have fixed my problems.


Out of interest what indicated speed do you get on your bikes and does it take a little while once past 105-110 to climb any further?

Thanks for all your help so far.
rubberfingers
Pit Bitch
Pit Bitch
 
Posts: 10
Joined: Tue Jul 28, 2009 6:23 pm

Re: Poor performance

Postby Yatsushiro » Fri Jul 31, 2009 12:51 pm

rubberfingers wrote:Out of interest what indicated speed do you get on your bikes


I don't think that there is many of us that run speedo's...

rubberfingers wrote:...and does it take a little while once past 105-110 to climb any further?


Only on my TDR :(
Paul
"I used to race, you know, but it was different in my day...
User avatar
Yatsushiro
Front Runner
Front Runner
 
Posts: 817
Joined: Tue Mar 24, 2009 1:57 pm

Re: Poor performance

Postby Dan Boy » Fri Jul 31, 2009 6:47 pm

Yatsushiro wrote:I don't think that there is many of us that run speedo's...


Wouldn't do you any good, you only look at your filler cap!!

D #72
Dan Boy
 


Return to Technical

Who is online

Users browsing this forum: No registered users and 2 guests

 

Who is online

In total there are 2 users online :: 0 registered, 0 hidden and 2 guests (based on users active over the past 5 minutes)
Most users ever online was 151 on Sat Sep 14, 2013 1:00 pm

Users browsing this forum: No registered users and 2 guests

Current time

It is currently Thu Nov 23, 2017 9:33 pm
RocketTheme Joomla Templates